United Airlines released a statement Monday after Flight 108, bound for Munich, Germany, had to turn back. The Boeing 787 with 219 passengers and 11 crew members had to retreat to Dulles International Airport after the left engine failed.

A United Airlines flight traveling from Washington Dulles International Airport made an emergency landing last month after the pilot declared a mayday call shortly after takeoff due to engine failure.

Mayday warnings happen regularly, say aviation experts—and both pilots and air traffic controllers are trained to know what to do.