A Southwest Airlines flight returned safely to Denver after an engine cowling fell off during takeoff on Sunday, the Federal Aviation Administration said, the latest in a spate of safety incidents involving Boeing.

The FAA said in a statement Southwest Airlines Flight 3695, a Boeing 737-800 passenger jet, returned to Denver International Airport "after the crew reported the engine cowling fell off during takeoff and struck the wing flap."

The plane, which took off at 8.15 am Sunday (1415 GMT) and was bound for Houston, was towed to the gate after landing and the FAA would investigate the incident, the US aviation authority said.

Southwest said in a statement to CNN that there were no injuries on board and apologized to passengers.

"We apologize for the inconvenience of their delay but place our highest priority on ultimate Safety for our Customers and Employees," CNN quoted Southwest as saying.

ABC News said the carrier had described the incident as a "mechanical issue" and said passengers were rebooked on other flights.

CNN, ABC and other US outlets broadcast videos taken by passengers that showed what appeared to be part of the cowling hanging off and flapping in the wind.

Boeing declined to comment publicly on the incident while Southwest did not responded immediately to AFP.

Boeing has been hit by a series of safety issues in recent months, the most serious coming in January when a fuselage panel on a Boeing 737 Max 9 Alaska Airlines jet blew off mid-flight in a near-catastrophic incident.

In March, a Boeing 777 jetliner bound for Japan had to make an emergency landing when a wheel fell off during take-off and landed in a San Francisco International Airport parking lot.

The Texas attorney general launched an investigation last month into Boeing supplier Spirit AeroSystems over recurring issues with some parts it supplies the US aviation giant.

Spirit AeroSystems manufactures fuselages and other large airplane parts, including for Boeing's 737 jets.

The announcement by Texas Attorney General Ken Paxton came only days after Boeing said some of its top executives, including CEO Dave Calhoun, were leaving the company.

Boeing has grappled with high-profile production problems and safety incidents involving its aircraft for more than a year.