WASHINGTON  At one time, airline safety generally meant one thing: avoiding a crash. But safety regulators are increasingly focusing on surviving one.

Starting this fall, all new airplanes will be required to have seats that will stay in place when subjected to stresses up to 16 times the force of gravity. The old seats had to meet stresses of only nine times the force of gravity. And, in a safety measure borrowed from automobiles, some seats will be equipped with air bags.

The combination of sturdy seats and air bags means that if a plane touches down short of the runway or rolls off the end of the runway and hits an obstruction, “You’re going to be conscious. You’re going to have the opportunity to survive,” said Bill Hagan, president of AmSafe, which makes the air bags.

In some airline crashes, the strength of the seats is irrelevant because the crash is not what the engineers call “survivable.” In other crashes, still violent but not as much so as exploding in midair or breaking up in flight, the passengers’ survival depends on suffering little or no injury in the first phase of the accident, as when a plane runs off the runway, and then getting out of the plane quickly to avoid a postcrash fire.