US airline authorities have launched an inquiry after an engine cowling on a Boeing 737-800 fell off during take-off, which resulted in damage to a wing flap.

After leaving for Houston, the Southwest Airlines flight returned to Denver International Airport safely around 8:15am local time yesterday, according to a BBC report.

BREAKING: Southwest Airlines Boeing 737 flight to Houston returns to Denver after engine cover tears away during takeoff pic.twitter.com/Z0uEjleor1

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Before landing, the aircraft, which carried 135 passengers and six crew members, ascended to a height of roughly 10,300 feet.

Videos posted on social media showed the removable metal covering of the plane's engine peeling off both during takeoff and in midair.

When the engine cover blew on Flight 3695, witness Lisa said passengers and crew felt like they were hit by a "bomb jolt", reports UK's Metro.

After the cowling, which covers the engine of the Boeing 737-800, fell off, Southwest Airlines announced that its maintenance teams would examine the aircraft. The airline confirmed that it was in charge of maintaining these parts, the BBC report said.

Federal Aviation Administration (FAA) records show that the aircraft was built in 2015. The 737-800 is an earlier version of the 737 from the most recent Max model.

The FAA said the Boeing aircraft was towed to the gate after landing.

Boeing declined to comment when approached by BBC, referring questions to Southwest for information about the airline's plane and fleet operations.

Boeing has been under scrutiny following a dramatic mid-air blowout in January, in which passengers on the flight from Portland, Oregon, to California narrowly escaped serious injury.