SAN FRANCISCO, Jan. 31 (Xinhua) -- Top U.S. defense and aerospace company Boeing on Wednesday announced the start of modification of MV-22 Osprey aircraft for U.S. Marine Corps under a multi-million U.S. dollar contract.

Boeing said in a statement that the Bell Boeing Joint Program Office has been awarded a 69.9-million-dollar modification to a previously awarded contract.

Bell Boeing will modify three existing MV-22 aircraft to improve the readiness and reliability of the fleet of tiltrotor aircraft for U.S. Marine.

"Our team is ready to take the MV-22 program into the future," said Kristin Houston, vice president of Boeing Tiltrotor Programs and director of Bell Boeing MV-22 Program.

Last week, the first MV-22 to be modified arrived at Boeing's Philadelphia facility where majority of the work will be completed.

Two additional aircraft will arrive within the next year.

The MV-22 Osprey is a multirole combat aircraft with both fixed-wing and rotary-wing capabilities that was primarily developed for the U.S. Marine Corps.

With both vertical takeoff and landing, and short takeoff and landing capabilities, MV-22 Osprey is designed to combine the functionality of a conventional helicopter with the long-range, high-speed cruise performance of a turboprop aircraft.

The aircraft, jointly produced by Boeing and Bell Helicopter, a Textron Company, went into active service in 2007.