Flying like a freed bird, the Marine Corps' V-22 Osprey helicopter-plane hybrid was in the air again Wednesday after being grounded for 18 months because of two fatal crashes.

The successful take-off, landing and take-off was off limits to television cameras, which later caught some in-flight maneuvers, including fast descents meant to determine whether changes in the hydraulics system and other alterations have corrected the problems that caused the earlier crashes. Chafed hydraulic lines could cause the V-22 to crash, according to the manager of the program.

The Osprey will undergo tests for more than a year before it is deemed safe for active duty, but that didn't stop 200 technicians, engineers and military watchers from cheering during the maneuvers at the Naval Air Station along Maryland's Patuxent River.

"It's gone well beyond our expectations," said Marine Col. Dan Schultz, the V-22 program manager. Schultz said the Marines, which lost 23 soldiers in December 2000 after two Ospreys crashed during test flights, hope to have the V-22 in service by December 2003.

The Osprey program was criticized when it was discovered that engineers doctored test results on the hybrid. Two officers received letters of reprimand in September.

Engineers attributed one of the crashes to vortex ring state, a phenomenon that can cause an aircraft to lose altitude quickly. Pilots now have alerts in place in the aircraft that will warn them of conditions that could lead to vortex ring state, Schultz said. They will also be taught how to maneuver to avoid or get out of VRS conditions.

Built by Boeing Co. and Bell Helicopters Textron, each V-22 costs $89.7 million. Only 20 have been built so far.

Wednesday's test flight, which was a test only of the helicopter functions of the Osprey, was conducted by pilots from Boeing and Bell Helicopter at Patuxent.

"So far this is going well. This is a perfect day," said Donald L. Byrne Jr., the Bell-Boeing V-22 contract director.

The Associated Press contributed to this report.