The powered portion of flight for an Atlas V boosting the third U.S. Air Force X-37B Orbital Transfer Vehicle (OTV) has successfully completed, according to Pratt & Whitney Rocketdyne officials.

The company makes the RL10 engine for the Centaur upper stage. The RL10 malfunctioned during the last U.S. Air Force launch in October owing to a fuel leak. Officials have not yet said how the leak occurred, though they know it happened when pressure in the chamber was at its peak.

Some Air Force officials say the service is lucky to have gotten the Boeing Global Positioning System IIF satellite into orbit when the leak occurred, though fuel reserves helped save the mission.

Meanwhile, the third Boeing OTV was boosted at 1:03 p.m. from Cape Canaveral on an Atlas V 501, which has a 5-meter fairing.

OTV is an unmanned spacecraft designed to maneuver in orbit and conduct a variety of experiments while also demonstrating reusability and the ability to quickly generate sorties.

The second OTV mission was in space for 469 days, and Air Force Space Command Gen. William Shelton praised it as a success. He did not provide details on its operations in orbit. OTV-1 spent 224 days in orbit.