"The Memory Trap," an espionage thriller by British author Anthony Price, contains this wry quote about airports: "The Devil himself had probably re-designed Hell in the light of the information he had gained from observing airport layouts." Whether you agree with Price or not (we suppose some people might find Heaven in the frenetic hub of their favorite airline), the observation captures the essence of the modern flying field: its complexity, its immensity and, of course, its density of people.
Any major airport has lots of customers, most of them passengers. For example, Hartsfield-Jackson Atlanta International Airport handles nearly 100 million passengers a year [source: Hartsfield-Jackson]. That's almost 20 times the number of people living in Atlanta itself and the same number of people living in a sizable country, say Ethiopia or Vietnam. Moving those people to their ultimate destinations requires 34 different airlines, which collectively make up the airport's 2,500 daily arrivals and departures. That's a lot of planes, a lot of passengers and a lot of airport personnel to make sure everything runs smoothly.
In many ways, a modern airport operates like a city. A governing body provides strategic direction and oversees day-to-day management. Waste removal crews collect trash from airport facilities and airplanes. Police and fire squads protect life and property. And various municipal-like departments handle administrative duties, ranging from human resources and public relations to legal and finance.
In addition to those activities, airports must also provide the resources necessary to care for a fleet of commercial aircraft. Airlines need space for airplanes, facilities for routine maintenance, jet fuel and places for passengers and flight crews while on the ground. Air-freight companies need space for loading and unloading cargo airplanes. And pilots and other crew members need runways, aircraft fuel, air traffic information, facilities for aircraft storage and maintenance, and places to relax while on the ground.
Throw in security concerns that arose after the Sept. 11 attacks, as well as capricious weather patterns, and you can see why job descriptions for airport managers often contain these kinds of descriptions: "You must have strong leadership and organizational skills, as well as excellent communication and interpersonal skills. This is not a position for the light-hearted and is stressful with long hours."
Luckily, our journey over the next few pages will give us a glimpse into the hidden world of airports without all of the attendant stress and nail-biting. Let's begin with a bird's-eye view.
Types of Airports: Small, Regional and Ridiculously Big
Most of us think AIRPORT, not airport, when we hear the term. We imagine massive sites covering hundreds of acres and filled with hangars, terminals, control towers and parking garages. In reality, many airports don't fit this description. Some are nothing more than a strip of grass, dirt or pavement placed in the middle of a farm or field. These so-called rural airstrips often serve just one or two pilots and don't have any other structures beyond the crude runway itself. Small community airports, on the other hand, may supplement a single airstrip with a few hangars and facilities to train student pilots, although they usually don't have operating control towers.
A regional community airport offers more, including a control tower and an automated weather observation system to provide pilots with real-time weather data. Such a facility usually has multiple Tee hangars -- simple metal enclosures -- and tie-down spots for permanently based or visiting pilots to house or stow their aircraft. A terminal building, with a pilot's lounge, restrooms, vending area and conference rooms, is often available, as is a fuel farm to provide either kerosene-based jet fuel or aviation gasoline (avgas), which is similar to automobile gasoline (mogas) but with some additives to make it perform better in spark-ignited internal combustion engines common in light aircraft. Because of its larger size, a regional community airport can accommodate a wider range of aircraft, from small prop planes to regional jets that seat no more than 20 passengers to larger three-engine jets, such as the Boeing 727, capable of seating up to 189 passengers.
In the U.S., most smaller airports fall into the category of general aviation [source: Airlines for America]. They don't handle military flights or common commercial transport but instead provide facilities and resources for personal flying, business flying, instructional flying and certain commercial flying activities, such as aerial photography and skydiving. Airports that handle passenger planes operated by companies such as Southwest, Delta and United Airlines and cargo planes operated by FedEx, DHL and other similar entities belong to the commercial aviation category. These large facilities are almost always situated near major urban areas, and they can handle national and international flights and support jumbo jets, such as 747s.
The United States boasts one of the world's most extensive aviation systems, with almost 20,000 small, medium and large airports. Nearly 17 percent of these make up the national airport system, which means they are eligible for federal assistance to go toward improvements that increase safety and security or that mitigate environmental impact. The national system includes a network of just over 500 commercial airports, all of which receive public funding and handle at least 2,500 passenger boardings a year [source: Airlines for America]. For the rest of this article, we will focus almost exclusively on these larger, more complex facilities.
Wanted Since the 1950s: Airport Sites
Commercial airports require huge amounts of land for runways and other facilities. As a result, few have been built in North America and Europe since the 1950s because metropolitan areas simply don't have any suitable sites. Even airports built on the outskirts of a city in the 1950s now find themselves hemmed in by urban and suburban development. This leaves planners with no choice but to renovate existing structures or expand within long-established property lines.
With that said, some cities have managed to add a commercial airport in the last couple of decades. Denver, for example, began construction of its international airport in 1989 and, after numerous construction delays, opened the facility in February 1995. Since then, it's grown to be the fifth-busiest airport in the United States, with more than 145,000 passengers passing through its gates each day [source: Denver International Airport].
Building a commercial airport on the scale of Denver's requires years of planning and a number of complex decisions. Here are some of the things airport planners must consider:
- Air transportation forecast: Planners use computer simulations and predictive modeling to make forecasts about an airport's anticipated traffic. They need to account for the number of arrivals and departures on a daily basis, but they also need to know the size of the aircraft that could potentially use the facilities because larger aircraft require longer runways. For example, large jets such as the Boeing 747 or Airbus A380 need about 10,000 feet (3,300 meters) to take off [source: Bowen and Rodrigue]. Based on this forecasted demand, planners make recommendations about the number and length of runways, as well as the size of airport terminals, all of which determines the amount of land required for a feasible project.
- Site location: As we've already mentioned, most commercial airports are located near major cities so workers and passengers can get to the facility easily. And yet most metropolitan areas have little or no land available for development on such a large scale. To find a site that can accommodate current needs and future growth, planners may seek property on the outskirts of a city, especially if rail and highway systems can provide adequate service between the airport and downtown areas. The tradeoff, of course, is availability of land. The Denver airport is almost 25 miles (40 kilometers) outside the center of the city, but the site gives planners a significant amount of elbow room. In fact, with its 53 square miles (137 square kilometers) of land, Denver International Airport is the largest airport in North America and the second-largest in the world (as of press time), with room enough to add six additional runways, another terminal and two additional concourses [source: Denver International Airport].
- Altitude: An airport's elevation can have an impact on its overall design. Air density is lower at high elevations, so longer runways are needed for an aircraft to achieve the necessary lift. Denver International Airport sits 5,431 feet (1,655 meters) above sea level, making it one of the highest airports in the U.S. Airfields in other countries must accommodate even higher elevations. For example, some South American airports, located in the Andes Mountains, are almost three times higher than Denver's.
- Topography: Runways require a smooth, level landscape with no obstructions. Planners must find naturally flat areas of land, or they must make them so by flattening hills or filling in swamps. These latter activities can increase construction costs considerably.
- Meteorological conditions: Airports built near an ocean experience much different weather patterns than those located inland or in mountains. For example, pilots flying into San Francisco's airport must often deal with thick banks of fog. In Orlando, they may deal with towering thunderstorms and wind shear. Airport planners must account for prevailing weather conditions when laying out runways and other structures.
- Environmental impact: Airports can have a lasting impact on the environment. They produce air and noise pollution and can impinge upon wetlands and rivers. The planning process often requires years of negotiation and stakeholder engagement to find and approve a site that satisfies the needs of community members (or at least a majority of them).
Once a site is chosen, planners must then design and lay out the airport's major structures. Much of their efforts center on how to best configure runways and terminals for the most efficient flow of traffic on the ground and in the airspace during departures and landings.
Airport Runways: Entering and Exiting the Friendly Skies
At its most basic level, an airport has just two parts -- an airfield and a terminal. The airfield consists of runways and ramps, known as taxiways, that connect to the terminal. When laying out runways, engineers borrow conventions used in navigation and surveying, fields that indicate direction with a compass reading. For example, the 0/360 position on a compass marks north; 90 degrees marks east; 180 degrees marks south; and 270 degrees marks west. Every runway has a different number, expressed in a shorthand format, painted at each end to designate its orientation. A runway facing due west on one end and due east on the other would be marked 27 and 9 respectively. A runway with a northwest/southeast orientation might be marked 31 on one side (short for 310 degrees), 14 on the other (short for 140 degrees).
The U.S. Federal Aviation Administration (FAA), which provides guidelines for airport layout, specifies 20 different ways to arrange runways, although many of these are variations on four basic configurations:
- Single runway -- When using this layout, airport engineers will orient the runway so aircraft can take advantage of prevailing winds.
- Parallel runways -- The distance between the two runways depends on the size and number of aircraft using the airfield. Close parallels have less than 2,500 feet between runways; intermediate parallels are between 2,500 and 4,300 feet (762 and 1,310 meters) apart; and far parallels are greater than 4,300 feet apart. Dual-line layouts feature two sets of parallels spaced 4,300 feet apart.
- Open-V runways -- Two runways that converge but don't intersect make an open-V layout. This arrangement gives air traffic controllers greater flexibility as they maneuver planes on the runways. For example, if no wind is blowing, they'll use both runways. But if the wind becomes strong in one direction, they'll shut down one runway and use the one that allows planes to take off into the wind.
- Intersecting runways -- Runways that cross each other are common at airports where the prevailing winds can change throughout the year. The intersection point can be in the middle of each runway, near the threshold (where aircraft touch down) or far from the threshold (where aircraft lift off).
To determine the length of a runway, airport planners consider a number of factors, including airport elevation, temperature, wind velocity, airplane operating weights, takeoff and landing flap settings and runway surface condition (dry or wet). A typical runway at a commercial airport, which must be able to accommodate jumbo jets, is between 10,000 and 12,000 feet (3,048 and 3,658 meters) long. Runways at small community airports, which serve aircraft with 20 or fewer passenger seats, may only be 3,000 to 4,000 feet (914 to 1,219 meters) long [sources: Bennett, Landrum & Brown].
Length isn't the only consideration. The runway surface itself must be much thicker than a highway to handle the extra weight of modern aircraft. Imagine a fully loaded Boeing 777 touching its wheels to the ground. That's 660,000 pounds (299,370 kilograms) coming down hard on the runway surface! Runways have to be specially constructed to take that strain without cracking or, worse, buckling. When the Denver International Airport was built, it took 2.5 million cubic yards (1.9 million cubic meters) of concrete to create five 12,000-foot (3,658-meter) runways, plus taxiways and aprons. First, 6 feet (1.8 meters) of compacted soil was put down; then, a 1-foot-deep (0.3-meter) layer of soil was spread, topped by an 8-inch- (20-centimeter-) thick cement-treated base; that was followed by 17 inches (43 centimeters) of concrete paving [source: Denver International Airport].
After landing, pilots use taxiways to get from a main runway to the terminal area, with its many gates. That's where we're headed next.
At the Hub of It All: Concourses and Terminals
At a busy airport like Atlanta's Hartsfield International, 2,500 flights take off and land every day. That means that, each day, perhaps as many as 250,000 people move through the airport and need certain services. Airports provide those services in their concourses and terminals, the heart of any airport. There you'll find the space for airlines to handle ticket sales, passenger check-in, baggage handling and claims.
Terminals come in many sizes and designs. At small airports, a single building holds a common ticketing and waiting area with several exits -- or gates -- leading to aprons, where aircraft park and boarding takes place. At large airports, this basic design can be expanded, which results in a linear or curvilinear terminal, often a very long building with plenty of room to accommodate ticketing and check-in and multiple gates for access to aircraft. In the 1950s, the linear concept evolved into the pier-finger terminal. In this configuration, passengers are processed in the main terminal and then directed down one of several piers, where aircraft await in gates known as finger slots. Concourses, the open areas formed where the main terminal building and the various piers meet, provide spaces for shops, restaurants and lounges.
The terminal complex at Atlanta's Hartsfield airport covers 130 acres -- that's 5.7 million square feet (529,547 square meters) of space available to handle all of the necessary aviation activities! The complex includes the domestic and international terminals and seven concourses. Within these concourses, there are 114 food and beverage vendors (most of these are owned and staffed by private companies), 90 retail and convenience stores (also owned and staffed privately) and 56 staffed service outlets (places where you can get your shoes shined or connect to the Internet) [source: Hartsfield-Jackson].
Hartsfield's concourses also lead to the gates. There are 207 gates in all (167 domestic and 40 international) [source: Hartsfield-Jackson]. The gates are where the airplanes park for passenger boarding and deplaning. Passengers wait in the immediate area of each gate to board the plane. Gates are rented by each airline from the airport authority, and some airlines may rent a whole terminal building in their "hub" airport, in which case the rental fee alone can run into the millions of dollars.
Routine airplane maintenance, such as washing, deicing and refueling, is done by airline personnel while the plane is parked at the gate. In some cases, other maintenance tasks might be performed at the gate, possibly with passengers onboard the plane – it's not uncommon to sit on a plane at the gate while maintenance personnel replace something like a hydraulic brake line on an aircraft.
Loading and Unloading Aircraft
Commercial airplanes are rarely flown empty, which means they must receive a few important items before they take to the skies. Cargo carriers load their planes with different types of freight -- packages and mail, perishable items, even human remains. Passenger airlines load civilian passengers, their luggage (and sometimes their pets), snacks and drinks. And, of course, both types of aircraft require fuel.
When you think of the size of an airport and the enormous volume of people it serves, you can imagine that providing these logistics services, as they're called in the industry, can be a daunting challenge. Consider baggage handling as an example. You can get the full scoop in How Baggage Handling Works, but we'll cover the essentials here to show the journey your checked bag takes from the ticket counter to the plane.
The first step, which occurs as part of the check-in process, is generating a bar code that includes information about your flight, including layovers and final destination. An airline attendant attaches this code to your bag and then places it on a check-in conveyor, which carries it away. A machine on the other side of the desk, armed with an array of scanners capable of "seeing" the bar code regardless of its angle, reads the encoded data and then routes the bag accordingly. Based on these instructions, your bag follows a continuous chain of conveyors, which both move it along rapidly and change its orientation as necessary. Additional scanners along the way check and double-check the bar code to make sure your bag continues to follow the right path. Eventually, your bag reaches human handlers, who load it onto a trolley and drive it to the plane, where it is loaded into the hold.
At the same time, an airline must keep track of the people flying on their planes. During the check-in process, an agent must scan an e-ticket or manually input passenger data, noting any upgrades (to first class, for example) or special needs (wheelchairs, infants, lap children). For international flights, agents must also enter a passenger's passport information. All of this data, plus a code for the final destination, appears on a boarding pass, which is printed out and given to the passenger.
At the gate, during boarding, the passenger hands the pass to another airline agent, who scans the barcode and confirms that person on the flight manifest. All passengers then pass through a door and onto a boarding bridge, or jet bridge, an enclosed, movable connector that links the gate area to the aircraft. When all passengers have boarded the aircraft, the agent prints a copy of the manifest so a member of the flight crew can check that all passengers successfully boarded. Once all passengers have been accounted for, the airline issues a final manifest, which can be used to notify relatives in the unlikely event of an air disaster.
After takeoff, the flight crew may offer food and beverage service. The food that passengers eat while onboard the airplane is usually provided by private companies contracted by one or more airlines at an airport. The food is prepared in a building that is off the airport grounds, shipped to the airport by truck and loaded onto the plane by the catering company's personnel. For example, LSG Sky Chefs is one of the catering contractors at Denver International Airport. They prepare and load thousands of meals per day for various airlines.
Airport Safety and Security
Airport security changed radically after Sept. 11, 2001. Before the terrorist attacks, private companies provided airport screening services. These companies worked under the guidance of the U.S. Federal Aviation Administration, and although their representatives scanned passengers using metal detectives and X-rayed bags, limited federal security requirements existed for cargo and baggage screening. After 9/11, the U.S. government established the Transportation Security Administration to improve and strengthen aviation security. By November 2001, the TSA was rolling out a number of new security measures: armed air marshals, reinforced cockpit doors and no-fly lists identifying people who could pose a threat and designating them for enhanced screening or, as appropriate, prohibiting them from boarding an aircraft.
Today, the TSA screens 100 percent of checked baggage for explosives. Most airports integrate this screening process into their baggage claim solutions. Using combinations of software, conveyance systems and screening technologies -- computer tomography, X-ray machines and explosive trace detection -- airports can now conduct full in-line screening without interrupting or delaying the movement of luggage from the ticket counter to the aircraft.
The TSA also subjects passengers to much more rigorous screening procedures that can involve pat-downs and whole-body scans. The latter involves so-called advanced imaging technology machines, which have been installed at some 200 airports since 2008 [source: TSA]. The machines come in two flavors, based on the type of electromagnetic radiation they use to make a scan. Backscatter machines send low-energy X-rays to bounce off a passenger's body. Millimeter wave (mmv) scanners emit energy more akin to microwaves. Both see through clothing to produce a 3-D image of the person standing in the machine, revealing any threats he or she may be trying to conceal. In either machine, the scanning process is the same. Passengers must remove everything from their pockets, as well as belts, jewelry, lanyards and cell phones. Then they step up a small ramp and, stand in the center of the machine, raise their arms, bent at the elbows, and remain motionless as the device completes a scan. For backscatter machines, the process takes about 30 seconds. For mmv scanners, it takes about 10 seconds.
Airports have also increased their on-site police forces since 9/11. At Los Angeles International Airport, for example, the police crew has grown from 100 sworn officers before the terrorist attacks to 430 today. This makes the airport force almost as large as others performing their duties out on the city streets [source: McCartney]. Some airport police are members of the city or municipality assigned to the airport, while others are from private security companies. Either way, their highest priority is thwarting a threat to a plane or to the airport itself. They question people who are photographing aircraft, conduct random searches of cars to turn up illegal guns and drugs, monitor traffic on the tarmac and around the terminals and investigate reports of theft at security inspection points. Many airports also use bomb-sniffing dogs to check out unattended bags, garbage cans and vehicles.
Airports complement their police forces with separate crews to handle fire and emergency medical services (EMS). An airport may have several fire/EMS stations on the ground because the FAA requires that emergency crews be able to reach the midpoint of a runway within 3 to 5 minutes. The crews are usually employees of the city or municipality and are stationed at the airport. At their disposal are specially designed and equipped fire and rescue vehicles capable of extinguishing jet-fuel fires with thousands of gallons of foam. These 44-ton, six-wheel vehicles can accelerate from 0 to 50 miles per hour in less than 35 seconds and come equipped with a variety of turrets, nozzles and booms to attack a fire efficiently and protect escaping passengers [source: Rosenblum].
Ground Transportation: Plane Train? Shuttle? Rental Car?
An airport can't exist in isolation. It depends on a massive surface-transportation system so that people can get to and from the airport, park and get from place to place within the airport structure itself. While your first thought about an airport is air travel, ground transportation is pretty crucial, too.
The busiest airport in the world is Atlanta's Hartsfield International Airport. You can take an extensive tour of Atlanta's ground transportation services on the airport's website, but here are some highlights of how ground transportation is critical:
- Roads allow access to and from the airport: In Atlanta, four interstate highways move traffic to and from Hartsfield. There's also a station for MARTA trains, which are part of the city's rapid transit system.
- Parking allows short- and long-term storage of automobiles. Parking can be on or off airport grounds, and some parking systems are run by private vendors under airport regulation. Hartsfield has more than 30,000 public parking spaces for its domestic terminal about 3,500 for its international terminal.
- Passenger drop-off and pickup areas make it easier for passengers to get into the terminals, although they're often plagued by traffic congestion because so many people are trying to get in and out.
- Rental car companies serve airports. Hartsfield has a dedicated rental-car facility with two four-story parking decks and 8,700 parking spaces. The center boasts a 137,000 square-foot service center where arriving passengers can rent vehicles from 13 rental-car companies.
- Shuttle services provide passengers with transportation to local hotels and off-site parking facilities.
- Private transportation is available in the form of limousines, vans and taxis.
- Public transportation (such as municipal buses and subways) may have stations at an airport. Besides the MARTA station at Hartsfield, 12 bus lines (public and private) serve the airport.
- Internal subway trains and trams may be available to help passengers get to the terminal gates from the concourse. Hartsfield's People Mover is a 3.0-mile (5.6-kilometer) loop track. The ATL SkyTrain, an elevated train, also connects passengers to the rental car center, the Georgia International Convention Center and hotels and office buildings.
In many ways, airports act as transportation hubs for entire regions. A person flies, say, from Washington, D.C., to Atlanta. After he arrives, he takes the SkyTrain from the main terminal to the rental car center. He rents a car, then drives downtown for a business meeting. In a little more than two hours, he has completed a trip that would have taken him 9.5 hours in a car. But think of the people, processes and modes of transportation he has engaged to make his quick trip. It's a highly complex system with hundreds, if not thousands, of moving parts and interconnecting strands. Managing all of this, as we'll see next, is a massive undertaking.
Not surprisingly, airports are huge businesses. How big? Well, Denver's airport cost about $5 billion to build, and operating costs are $160 million per year. But its economic impact on the state is huge. According to the Colorado Department of Transportation, Denver International Airport generates $22.3 billion for the state every year [source: Denver International Airport].
Commercial airports are publicly owned and generally financed through municipal bonds. Airports typically own all of their facilities and make money by leasing them to airlines, air-freight companies, and retail shops and services, as well as by charging for services like fuel and parking and through fees and taxes on airline tickets. The revenues pay off the municipal debt and cover the operating costs. Airports often require other sources of funding as well, such as airport bonds and government grants. But most airports are self-sustaining businesses once they become operational.
About 90 percent of employees at airports work for private companies, such as airlines, contractors and concessions [source: Airlines for America]. Most of the remaining 10 percent work directly for the airport as administrators, terminal- and grounds-maintenance personnel and safety crews. Air traffic controllers are employees of the federal government. Airports have their own departments of finance, personnel, administration and public relations, much like any city or municipality.
Whether or not you find heaven or hell in the complex world of a commercial airport largely depends on your personality and the circumstances of your travel. A business person trying to make an early-morning meeting tomorrow will likely curse the airport today if her flight is delayed or she has to make a mad dash across two miles of terminal to catch a connecting flight. Someone taking a month-long vacation to Hawaii may be much more forgiving about these realities of flying and may even see the airport as a great place to observe people and study human nature. Either way, airports will continue to be all-important nodes in the international transportation system -- at least until someone perfects teleportation.
Drone pilots have to learn to fly drones somehow. Find out if drone pilots train using video games at HowStuffWorks.
Author's Note: How Airports Work
I'm definitely one of those people who flies less now than before Sept. 11. And not because I'm afraid of terrorists flying the plane into a building (although that would suck). For me, dealing with airport security and the frequent delays, especially after you've already boarded, makes a long drive seem like a rational alternative.
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