An engine cover on a Southwest Airlines Boeing 737-800 fell off on Sunday during takeoff in Denver and struck the wing flap, prompting the Federal Aviation Administration (FAA) to open an investigation.
No one was injured and Southwest Flight 3695 returned safely to Denver International Airport around 8:15 a.m. local time (1415 GMT) on Sunday and was towed to the gate after losing the engine cowling.
The Boeing aircraft bound for Houston Hobby airport with 135 passengers and six crew members aboard climbed to about 10,300 feet (3,140 m) before returning 25 minutes after takeoff.
Passengers arrived in Houston on another Southwest plane about four hours behind schedule. Southwest said maintenance teams are reviewing the aircraft.
The plane entered service in June 2015, according to FAA records. Boeing referred questions to Southwest.
