The Boeing 787, flying from the Washington, D.C., area to Munich, had to make a hasty return to the airport "to address a mechanical issue," United said.

Flight 108, carrying 230 people, was only moments into its ascent when its pilot reported the mid-air emergency to air traffic control.

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.