Bobby Lewis(DENVER) — After their United Airlines plane departed from Denver headed to Orlando, Florida early Sunday morning, passengers aboard Flight 293 looked out their window to a frightening sight: an engine cover had broken loose and was flapping around, leaving the engine exposed.

Half an hour after taking off, pilots asked air traffic controllers at the Denver International Airport to return to the airport, saying that, “an engine panel has become detached from the airplane.”

Passengers said they were relieved and grateful for what they said was the pilots’ quick response.

“The pilot really took some heroic action,” Kahlin Grant said. “He made a big decision to turn us around quickly, he essentially saved some lives.”

In a statement, United said that the flight “returned to the airport due to a mechanical issue with one of the engines.” According to experts, the purpose of the engine cover is mostly aerodynamic and does not necessarily affect the operation of an engine.

This is not the first time a flight has been diverted by a problem with an engine cover coming loose. Last November, a Frontier flight returned to the airport in a similar incident.

In another incident last year involving a United jet, an entire engine cover was ripped off in mid-air on flight to Hawaii.

Despite these incidents, it is still rare for planes to divert because of mechanical or other problems. According to the Bureau of Transportation Statistics, from July 2018 until July 2019, less than one percent of flights were diverted.

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