A Marine Corps MV-22B Osprey (bureau number 165844) crashed in Morocco on April 11, killing two U.S. Marines and injuring two more severely.

The tilt-rotor aircraft was deployed as part of the 24th Marine Expeditionary Unit Aviation Element and was flying from the amphibious assault ship USS Iwo Jima. The aircraft had just dropped off Marines in a training area and was taking off when the crash occurred.

The Marines were participating in African Lion, a bilateral exercise with the Moroccan military run by U.S. Africa Command. About 1,000 Marines and 200 other U.S. military personnel were participating. The MV-22B was reported to be carrying two pilots and two flight engineers.

Neither the cause nor circumstances of the accident were immediately available.

The aircraft belonged to squadron VMM-261 “Raging Bulls,” commanded by Lt. Col. Brian C. Smith, part of the 2nd Marine Aircraft Wing at Marine Corps Air Station New River, North Carolina.

A different Osprey made a precautionary landing near Amarillo, Texas – where final assembly of the aircraft takes place – when an instrument panel warning light came on. This incident was considered routine.

No Marine Corps Osprey had been involved in a fatal mishap for more than a decade, although an Air Force CV-22 crashed in Afghanistan in April 2010, killing four, under circumstances that are still in dispute. Prior to the crash, the Osprey was rated as the safest rotorcraft in Marine Corps inventory, based on “Class A” accidents, meaning mishaps involving a fatality or permanent disability or more than $2 million in damage.

Following the Morocco incident, the Osprey ranks behind the AH-1Z Viper attack helicopter, which has had no accidents, and the long-serving CH-46E Sea Knight. Taken together, Marine Corps and Air Force Ospreys have logged about 130,000 safe flying hours, the Marine Corps says. Neither service branch grounded its Ospreys after the crash, which is not expected to affect future operations by the tilt-rotor aircraft.