The engine cover of a Boeing aircraft fell off, leading to an investigation

US airline regulators have launched an investigation after a Boeing 737-800's engine cowl fell off during takeoff and struck the plane's wing.

The Southwest flight returned safely to Denver International Airport at approximately 08:15 local time (15:15 GMT) after originally departing for Houston.

The plane had 135 passengers and six crew members on board and rose to about 10,300 feet (3,140 meters) before landing.

The accident comes amid manufacturing and safety concerns at Boeing.

Southwest Airlines said its maintenance teams will review the Boeing 737-800 after the plane's hood covering the plane's engine fell off. The airline confirmed that it is responsible for maintaining these parts.

“We apologize for the inconvenience caused by the delay, but we place the highest priority on the utmost safety of our customers and employees,” a statement said.

Built in 2015 according to FAA records, the 737-800 is a previous generation 737 of the latest Max model.

The plane in the latest accident was powered by CFM56 engines, while the 737 Max models use the CFM-Leap engine. Both are made through a joint venture between GE Aerospace and Safran Aircraft Engines

The Federal Aviation Administration said the Boeing plane was towed to the gate after landing.

Boeing declined to comment when contacted by BBC News, and referred questions to Southwest for information about the company's aircraft operations and fleet.

Southwest said it would put passengers on another plane to Houston, about three hours later than scheduled.

Boeing has come under scrutiny following a dramatic mid-air explosion in January, in which passengers on a flight from Portland, Oregon, to California escaped serious injuries.

Regulators temporarily grounded nearly 200 Boeing 737 Max 9 planes after a door seal fell off the Alaska plane shortly after takeoff.

Boeing has been trying to repair its reputation for years after two crashes of a variant of the 737 MAX in 2018 and 2019 that killed 346 people.

Subsequently, its popular 737 MAX aircraft was grounded globally for more than 18 months.