Above field elevation, a certain altitude above that specified for the airport.

Plane hits a certain altitude, the bomb goes off.

It was designed to be put on board an aircraft and to explode when a certain altitude was reached.

"In the rocket we turn off the motors at a certain altitude," Tom said, "and keep on flying along our orbit."

Above a certain altitude, even pure oxygen wasn't enough.

They fire a red, incendiary projectile that bursts at a certain altitude.

"Once the artillery reaches a certain altitude it explodes into fragments," he said.

Coffee also grew best at a certain altitude, whereas indigo flourished almost anywhere.

It requires a large source of energy at a certain altitude to maintaining a significant hydrodynamic escape.

"I know we're supposed to fly a certain direction at a certain altitude."