A Southwest Airlines jet returned to Denver on Sunday morning after an engine cover came off and struck a flap during takeoff, according to the Federal Aviation Administration (FAA).

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

“We apologize for the inconvenience caused by their delay, but we have the ultimate safety of our customers and employees as our top priority. Our maintenance team is inspecting the aircraft,” the statement read.

This is the second incident in a week for the airline, which canceled a flight from Texas on Thursday (March 4) after reports of an engine fire.

The Lubbock, Texas, fire department confirmed online that a fire broke out in one of the two engines and needed to be extinguished.

The FAA is investigating both incidents.

Both aircraft are Boeing 737-800s, which are older models than the 737 Max.