WASHINGTON, March 18 (Reuters) - Investigators found

that two key navigation parts failed on a United Airlines

flight from Lagos to Washington on January 24, causing

the plane to lurch suddenly and injure several passengers.

The National Transportation Safety Board said the left and

then right inertial reference units failed on the Boeing

787 jetliner, which was followed by the autopilot disconnecting

automatically and sudden altitude changes. There were 16

injuries, including one serious injury. The flight returned to

Nigeria.

United declined to comment. Boeing ( BA ) did not immediately

comment.

The safety board said the flight movements lasted for 12

minutes at 36,000 feet (11,000 meters) over Côte d'Ivoire. At

the time, flight attendants were serving meals in the cabin.

Investigators removed the flight recorders and other

equipment from the aircraft in Lagos and sent them to Washington

for the safety board to inspect.