A Southwest Airlines flight out of Denver International Airport had to make an emergency landing after an engine cover fell off during takeoff.

According to the New York Times, the Boeing 737-800 was supposed to fly to Houston on April 7 before an engine cowling came off and hit the wing flap. The plane and its 135 passengers and five crew members landed safely back in Denver with no reported injuries. 

Southwest Airlines has its maintenance teams looking over the aircraft, while the Federal Aviation Administration says it plans to investigate the incident.

This comes as Boeing faces a lengthy list of issues, dating back to the blowout of a door plug on an Alaska Airlines 737 Max 9 on January 5, followed by several other incidents on United Airlines Boeing planes in March. That included a Boeing 777 that had to make an emergency landing in Los Angeles after it lost a tire, and another 777 out of San Francisco that had to turn back for a hydraulic leak. 

Boeing paid Alaska $160 million in initial compensation on April 4 for the blowout incident, with more payments expected down the line.