Southwest Flight From Denver , Loses Engine Cover. On April 7, a Boeing 737-800 plane in use by Southwest Airlines lost an engine cover which hit the wing flap, the Federal Aviation Administration said. . According to air traffic control audio, a pilot said that "several passengers and flight attendants heard something loud hit the wing.". After determining the issue, the plane safely returned to Denver, and Southwest issued an apology. . We apologize for the inconvenience of their delay but place our highest priority on ultimate Safety for our Customers and Employees, Southwest Airlines, via statement. There were no reports of injuries. . According to FAA records, the plane was last certified to be airworthy in May of 2015. The agency will investigate the incident. . Boeing refused to comment and instead pointed to Southwest for details "about plane and fleet operations," CNN reports. . The incident is just the latest in a series of mechanical issues Boeing has experienced over the last several months.