A Southwest Airlines plane returned to Denver on Sunday morning after an engine cowling fell off and hit the wing during takeoff, according to the Federal Aviation Administration.

Southwest Airlines said in a statement that the Boeing 737 aircraft landed safely and passengers headed to Houston were transferred to another plane.

We apologize for the inconvenience caused by the delay, but we prioritize the safety of our customers and employees above all. The statement said our maintenance teams are reviewing the aircraft.

This is the second incident the airline has faced this week, as a flight from Texas was canceled on Thursday following a report of an engine fire. The Lubbock, Texas Fire Department confirmed online that a fire broke out in one of the engines that required extinguishing.

The Federal Aviation Administration is investigating both incidents.

Both planes were Boeing 737-800 models, which are an older version than the 737 Max model.