The inquiry announced on Thursday was the latest chapter in a saga that saw 23 Marines die in two MV-22 crashes last year and the grounding of the aircraft, known as the "Osprey", which takes off like a helicopter and flies like a normal airplane.
Lt. Col. O. Fred Leberman, a 20-year Marine Corps veteran, was relieved of his duty as commander of Tilt-Rotor Training Squadron-204 in New River, North Carolina, and a team headed by the corps' inspector general started the inquiry based on an anonymous letter and tape.
"In light of the ongoing inspector general's investigation, it is inappropriate for me to comment on the tape recording and letter in 60 Minutes' possession," Leberman said in a statement to CBS television network's 60 Minutes program.
"I can assure the American public and the Marine Corps the matters currently under investigation did not cause the most recent accident," he said, adding:
"I am confident the pending investigation will prove the comments on the tape and in the letter are taken out of context and in no way compromised the safety of any Marines -- or the integrity of the Osprey program."
But while Leberman refused to appear on 60 Minutes to discuss the Osprey, many others were willing to do so.
And he added, "There are no free lunches in aviation, period. And this aircraft is a perfect example of it. It is a hybrid. A cross breed, if you will. It's part helicopter, its part wing-fixed. As such it will never been an excellent helicopter or an excellent fixed-wing."
The district of Republican Congressman Curt Weldon of Pennsylvania includes Ridley Township, where the Boeing company builds the Osprey's fuselage. He has flown on the Osprey nd maintains the aircraft, which brings 1,500 jobs to his district, is safe.
"We're pushing the envelope of technology," Weldon said. "When you push the envelope, there is risk associated that you have to attempt to deal with. Now, would we like to eliminate that totally? Absolutely. But, I am convinced that this aircraft does not have a technology problem."
Donna Harter's son, Kelly, was one of the 19 Marines killed when an Osprey crashed in Arizona last July. She said her son was a crew chief in charge of maintenance for the aircraft. And he told her about the problems his unit was having with it.
"It cannot do the missions they want it to do, and they cannot use another Marine for a test," Harter said.
"They used my son for a test and he's gone. And I don't want to see it happen to another family."
In a November 30 briefing, Brig. Gen. James F. Amos, deputy assistant commandant for Marine Corps Aviation, said that in the first 13 days of November, the mission-capable rate or percentage of Ospreys available for service on a given day averaged 73.2 percent.
But handwritten logs 60 Minutes received show that only 38-percent of the Osprey were able to fly during the period.
On the audiotape, even the aircraft's mechanics were worried that the pressure to falsify data could lead to a crash.
- "The way we are having to do things lately, it's gonna be real easy for one of us to missing something. And I, I-- that's the feeling that I have in my gut right now. And that-- that's not good to have."
While the Marine Corps now admits maintenance records were falsified, as recently as Friday, it still insisted that there is no relationship between the falsifications and any of the Osprey crashes.
The fatal crashes last April 8 during a night training mission in Arizona and Dec. 11 in North Carolina raised key questions about the aircraft's safety. All 19 Marines aboard an MV-22 died in the April crash and all four crewmen were killed in the North Carolina incident.
The Marine Corps said last month the MV-22 that crashed in North Carolina suffered a "hydraulic malfunction", but that it was not known if the problem was linked to the crash during a night training flight. Hydraulic pressure is used by pilots to maintain control of aircraft in flight.
The information obtained by 60 Minutes indicates that at least two of the remaining eight Ospreys appear to have serious hydraulic problems.
The two crashes prompted Defense Secretary William Cohen in December to order an investigation into the $40 billion MV-22 Osprey program. Immediately after the North Carolina incident, the Marine Corps postponed a decision on whether to begin initial full-scale production of the MV-22.
The Osprey is built jointly by Boeing Co. and Textron Inc.
©MMI Viacom Internet Services Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Reuters Limited contributed to this report