Airplanes almost always have to refuel between flights, and jumbo jets love fuel. A 747 can consume about 1,000 gallons of fuel on an international flight, say from Malaysia to the United Kingdom [source: Park and Rothman]. "Filling up the tanks" takes tens of thousands of gallons of fuel, which means that a busy airport can sell millions of gallons of gas every day. In some airports, fuel trucks carry fuel from the storage depot to the airplane for refueling. In others, fuel is pumped through underground pipes directly to the terminals.
Jets don't use the same type of fuel you pump into your car. Their engines need something with a bit more kick -- something with good combustion characteristics and a high freezing point. Today's aviation fuels are made from different grades of kerosene. Jet A-1 fuel has a flash point (the lowest temperature at which the liquid can evaporate enough to combust) of 100 degrees Fahrenheit (38 degrees Celsius) and a freezing point of minus 53 degrees Fahrenheit (minus 40 degrees Celsius). Jet A fuel, available only in North America, has the same flash point but a higher freezing point.
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.