Defense Secretary Leon Panetta shoved his head into a snug aviator helmet topped with goggles one September morning and swooped into Lower Manhattan on a V-22 Osprey, a $70 million aircraft that Marines use for battlefield assaults in Afghanistan.

“How’d you like that gizmo?” Panetta said after landing at the Wall Street heliport in the Osprey, which takes off like a helicopter, flies like an airplane — and has claimed the lives of 30 people in test flights.

Defense Department officials say the hybrid aircraft was the fastest way to get Panetta and his entourage to New York that day. But anyone who has followed the tortured history of the Osprey saw the persistent, politically savvy hand of the Marines in arranging Panetta’s flight — and another example in what has become a case study of how hard it is to kill billion-dollar Pentagon programs.

“At a car dealership, what the salesman wants to do is get you inside the vehicle,” said Dakota Wood, a retired Marine lieutenant colonel and defense analyst. “You take the test drive and wow, it’s got a great stereo, it feels good, it has that new-car smell.”

That flight with Panetta, he said, is “an insurance policy against future defense cuts.”

As a joint congressional committee appears paralyzed days from a deadline to agree on a plan to cut the nation’s deficit, the Pentagon is vulnerable to forced reductions over the next decade that would slash its spending by $500 billion, on top of $450 billion in cuts already in the works — a total of more than 15 percent of its operating budget.

But as Panetta considers scaling back major weapons programs, the Osprey illustrates the challenges in downsizing the world’s most expensive military. The aircraft has survived after repeated safety problems during testing, years of delays, ballooning costs and tough questions about its utility.

Even Dick Cheney, when he was the defense secretary under the first President George Bush, could not kill it.

“Don’t bet against the Marines as budget warriors,” said Richard Aboulafia, an aviation analyst at the Teal Group in Fairfax, Va.

In just the last few weeks, the commandant of the Marine Corps, Gen. James Amos, has talked up the Osprey at the Council on Foreign Relations and in written testimony to Congress, branding the aircraft “revolutionary” and the arguments of its critics ill-informed. The contractors who built the aircraft have been running advertisements in defense industry and news publications in Washington, celebrating its 100,000 flight hours and lauding it as the “safest Marine rotorcraft” of the last 10 years. Reporters have been flown on Osprey media flights, including with Panetta to New York.

One of the Osprey’s biggest defenders on Capitol Hill, Rep. William Thornberry, R-Texas (the aircraft is assembled in his district), said in a recent interview that the Osprey was much improved and “not where it was five or 10 years ago.” He also said that one of the Osprey’s biggest critics in Congress, Rep. Lynn Woolsey, D-Calif., “doesn’t have a clue what she’s talking about.”

Thornberry was referring to Woolsey’s comments on the House floor in May, when she called the Osprey “a poster child for the excesses and inefficiencies of the military-industrial complex” and offered an amendment to kill its financing. The measure failed, but an aide to Woolsey said she remained steadfast in her opposition.

Defense industry analysts say that the number of Ospreys could well be cut back from the 458 expected to be bought by the Marines, the Navy and the Air Force, but that the program is so far along it is unlikely that the Pentagon or Congress will kill the Osprey entirely. (The far bigger target is the F-35 Joint Strike Fighter, the most expensive weapons program in history.) Nearly 300 Ospreys are already in service or in production, and some $36 billion out of a projected $54 billion has been spent.

“We’ve gone this far, we may as well make the most of it,” said Aboulafia, who said the Osprey had overcome its earlier problems — the last test-flight crash was more than a decade ago — and was a “good aircraft,” although costly.

He credited the contractors, Bell Helicopter Textron and Boeing, but particularly the Marines, for a relentless lobbying and public relations campaign.

That campaign spanned 25 years and went into overdrive when Cheney, under orders from President George H.W. Bush to cut military spending, tried to cancel the Osprey. He said it was too expensive (at the time, the program was projected to cost $28 billion for 682 aircraft) for what he viewed as the Marines’ relatively narrow mission, amphibious assault.

But the Marines saw the aircraft as crucial to their survival as a quick-response, expeditionary force. In arguments they still make today, the Marines pressed their case that the Osprey could take off from aircraft carriers and get in and out of difficult landing zones better than airplanes and faster than helicopters, carry more people and save lives. In response to Cheney, they led a fierce counterattack, meeting with lobbyists and supporters in Congress in secret strategy sessions on Capitol Hill.

“It bordered on insubordination that the Marines conducted themselves the way they did,” said Richard Whittle, the author of the definitive book about the program, “The Dream Machine: The Untold History of the Notorious V-22 Osprey.”

“The secretary of defense had said, ‘We’re killing this program,’ ” Whittle said, “and the Marines were plotting behind the scenes with his opponents.”

Led by Textron lobbyists and Curt Weldon, then a Republican representative from Pennsylvania whose district included a Boeing helicopter plant where the vehicle’s fuselage was built, the group briefed members of Congress about the jobs the Osprey would bring to their districts, offered congressional trips to Osprey factories, held Osprey lunches, pushed for Osprey hearings and organized a pro-Osprey coalition of business leaders.

“We pulled out all the stops,” Weldon recalled in a recent interview. The Marines now say the aircraft survived on its merits, not because they took on Capitol Hill. But their campaign was a near-legend in the industry — and could be invoked in the military budget battles to come.

Cheney eventually admitted defeat, and the Osprey endured even through its test crashes and groundings in the 1990s. By 2007 it finally went into service, in Iraq, where Gen. John Kelly, then the commander of the Marines in Anbar province, oversaw the first two squadrons of Ospreys in combat. The speed of the aircraft “turned a province the size of Texas into Rhode Island,” he recalled.

Kelly is now Panetta’s senior military assistant, and it was his idea to fly the boss to New York by Osprey. Although Kelly is an Osprey enthusiast, he insisted that his goal was not to sell Panetta on the aircraft, but to solve the logistical problem of getting him to the Sept. 11 memorials in New York and Shanksville, Pa., and back to Washington all in one day. It was too far for a helicopter, and taking a plane would have required too much time for ground transport.

“The only real way to do it was in Ospreys,” Kelly said.

Not that Panetta was initially enthusiastic.

“He, like everybody, has this thing in his mind — ‘Oh, this is this death trap,’ ” Kelly said.

But Panetta, who got a splendid view from the jump seat between the Osprey’s two pilots, “loved it,” the general said. It did not hurt that one of the pilots had flown an Osprey that rescued a downed American pilot in Libya in March and kept the defense secretary transfixed with stories from the front.

No one knows what, if anything, Panetta will decide about the V-22 as he pores over the Pentagon’s books. But Defense Department officials say he is still talking about his ride. As he told reporters that day: “Interesting way to fly.”