If Cars Have Shoulder Seat Belts, Why Not Airplanes?

"The reason you must wear a seat belt, flight crew included," Heather Poole, an American Airlines flight attendant and author, told The Telegraph in 2015, "is because you don't want the plane coming down on you. People think they're lifted up in the air during turbulence. The truth is the plane drops. It comes down hard and it comes down fast and that's how passengers get injured — by getting hit on the head by an airplane."

It's simple physics, Newton's first law of motion: A body at rest will remain at rest unless an outside force acts on it.

Think of it this way: If you're not wearing a seat belt on an airplane that drops suddenly — which often happens with turbulence — you're the one at rest. You'll stay at rest as the plane, very literally, drops out from under you. If you're strapped in, the seat belt serves as an outside force acting on you, taking you with the plane as it drops and saving you from bonking your head on that overhead bin above you.

"It allows you to stay in place and ride along with the airplane," McSpadden says. "It's just that added safety margin that if something unexpected happens, you're still going to stay with the airplane."

A little reasoning might suggest that if a lap belt is good while flying, a shoulder harness — like those in cars and those in smaller so-called general aviation planes — would be even better. Indeed, shoulder belts or harnesses might help, McFadden and others say.

But they would be costly to install, and trickier to get to work correctly on bigger commercial planes, experts say. They'd probably be uncomfortable on longer flights. And wearing shoulder harnesses might meet a lot of resistance from the flying public, too.

"The answer would be, yes, it certainly would help, because it would prevent the movement of the upper torso aggressively in terms of some kind of sudden impact," McSpadden says. "How you can do that is another question entirely."

Some wonder whether shoulder belts are needed on commercial airlines, considering lap belts — when they're used — seem to do the trick. "Clearly for the vertical deceleration [typical] of an airplane crash, the lap belt seems to be the most important restraint," David King, a trauma surgeon at Massachusetts General Hospital, told Time after the July 2013 wreck of Asiana Airlines flight 214 in San Francisco killed three people. (Noted in the official National Transportation Safety Board report of that accident: "The two ejected passengers (one of whom was later rolled over by two firefighting vehicles) were not wearing their seatbelts and would likely have remained in the cabin and survived if they had been wearing them.")

In smaller aircraft, though, shoulder harnesses — which are required for all seats in all small airplanes manufactured since Dec. 12, 1986 — work and work well. Used with lap belts, shoulder harnesses in smaller planes have been shown to reduce serious injuries from accidents by 88 percent and fatalities by 20 percent, according to the Federal Aviation Administration (FAA).

Ironically, the safety record of commercial airlines may be the overwhelming reason that shoulder harnesses have not been required of large passenger planes. In 2017, no one was killed in a commercial jet airliner incident anywhere in the world, making it the safest year ever for big passenger planes. In its Civil Aviation Safety Review for 2017, which examined accidents on large passenger aircraft, the Dutch aviation consulting firm To70 estimated that there were "0.08 fatal accidents per million flights [in 2017]. That is a rate of one fatal accident for every 12 million flights."

With a safety record like that, it's hard to argue that shoulder harnesses would lower the risk of flying enough to offset the costs, the effort and the resistance such a major change would generate.

Lap belts, though? They help. They help a lot. So when flying, it's probably best to buckle up and stay that way. For your own good.