May 11 (Reuters) - The Federal Aviation Administration said on Monday that it had approved Boeing's protocol for safely returning MD-11 airplanes to service in the U.S. after barring flights in December following a fatal crash in November of a UPS cargo plane in Kentucky that killed 15 people.

UPS opted to retire its MD-11 fleet after the fatal crash but FedEx said it plans to resume the use of its fleet of 28 MD-11 planes later this month after they are in compliance with the Boeing maintenance requirements.

(Reporting by David Shepardson; Editing by Mark Porter)