The passenger jet was responding to an alert of another aircraft in the vicinity, federal authorities said. A Cold War-era military plane was nearby at the time.

A person on the flight said that it “dove aggressively” and that people flew out of their seats. The flight landed safely at its destination, Las Vegas.

Two flight attendants on a Southwest Airlines Co. jet were injured Friday after the pilot had to maneuver sharply in response to alerts that another aircraft was in the vicinity.