A Boeing 787-8 Dreamliner, operated by United Airlines, experienced a mid-air scare in the US last week owing to a critical engine failure, media reports said.

The Munich-bound United Airlines Flight UA108 was flying out of Washington Dulles Airport on its scheduled transatlantic journey on July 25, when its left engine failed.

The incident prompted the crew to declare a "MAYDAY".

The engine malfunction was reported shortly after the flight departed from Washington Dulles and reached an altitude of 5,000 feet.

The crew declared an emergency soon and worked closely with air traffic controllers to ensure a safe emergency landing.

According to data from FlightAware, the aircraft remained airbound for 2 hours and 38 minutes, circling northwest of Washington in a holding pattern to safely dump fuel before landing back at Washington Dulles Airport.

During this time, the United Airlines pilots requested air traffic controllers (ATC)  for fuel dumping while maintaining an altitude of  6,000 feet to manage the plane's weight and entered a holding pattern northwest of Washington, a report by aviationa2z said.

After landing, the Boeing aircraft could not move on its own and had to be towed off the runway due to the disabled left engine.

It remained grounded at Washington Dulles Airport as of Monday.

There were no injuries in the incident, and the technical malfunction is expected to be investigated further.