A Singapore Airlines flight to Beijing was forced to turn back shortly after departing Monday because of an abnormal noise in the cockpit, the carrier said.
"Shortly after departure, pilots reported an abnormal noise in the cockpit and elected to return the aircraft to Singapore for investigation," the airline said.
The carrier said an investigation found the noise was caused by a seal on the nose landing gear door of the Boeing 777-200 jet. It said the seal does not affect operation of the landing gear itself.
Passengers were transferred to another aircraft and the flight resumed, it said.
"The safety of our customers and crew is our primary concern, therefore the captain did the right thing to turn back the aircraft to allow for investigation of the cause" of the noise, the airline said in a statement.