The Malaysia Airlines Boeing 777, which was on its way to Kuala Lumpur, took off at 1:55pm from runway number one at Arlanda. People on the ground reported that the plane appeared be dropping metal pieces, and contacted the airport authorities.
The pilot on Flight MH091 had not noticed any faults, the Swedish Search and Rescue Service said, but added that a warning light had indicated a problem with the engine on the port side.
The pilot decided to return to Stockholm, and dumped fuel over the Baltic Sea before turning back to Arlanda.
The plane landed without problems at Arlanda at 2:47pm. A major emergency operation then swung into effect.
For planes to lose engine parts in this way is unusual, according to Niclas Härenstam, spokesman for airport operator LFV. He said the incident would be investigated.
An experienced pilot told Christina Lindber, editor of Swedish flight industry magazine Flygrevyn, that the problem could have been caused by a collision with a bird or through an object on the runway getting stuck in the motor. It was unlikely for ice to have damaged the engine, she said, as the engines on a Boeing 777 are under the wings.
The runway from which it took off was later closed by airport authorities, and airport staff found bits of metal and insulation material.
“The objects come from the engine,” Härenstam confirmed.
Flight traffic from the airport was not affected.
The 300 passengers onboard the plane were due to be rebooked by Malaysian Airlines. The Boeing 777 is classed as a modern passenger plane. The first model was delivered in 1995.