The Alpine Republican aggressively supported the program over two decades even though the Pentagon repeatedly questioned the jet's feasibility and lambasted the contractor's work.

Hunter has received $36,000 in campaign contributions from duPont Aerospace, which began receiving congressional funding for the aircraft in 1988. Hunter had been chairman of the Armed Services Committee before Democrats gained control of the House this year. He is running for the 2008 Republican presidential nomination.

DuPont has long promised that the plane, the DP-2, will have the ability to take off and land vertically, fly faster and farther and carry more troops than aircraft now used for similar tasks. For just as long, military officials have said it would never work as envisioned.

Prototypes have barely gotten off the ground in hover tests and suffered damage from “hard landings” and other mishaps.

Hunter, defending his support for the program yesterday before the House Science and Technology Committee's investigations and oversight subcommittee, said the DP-2 “represents potential leap-ahead technology to support our Marines and Special Forces. . . . The idea around here that if the Pentagon doesn't come up with something, that if the services don't like it, you're not going to build it, is ridiculous.”

Rep. Brad Miller, D-N.C., who chaired the hearing, noted that the DP-2 “is still not operational and has never received a positive technical review in more than 20 years. Congress appears to have permitted the DP-2 program to become a hobby, not a serious research project.”

The aircraft has received $63 million in taxpayer funds – entirely through earmarked congressional spending – despite a series of Pentagon and NASA studies that from the beginning found fault with the project. Earmarks are line items inserted into congressional spending bills at the request of individual congressmen without public debate, discussion or disclosure.

At the hearing, Hunter gave no ground defending his use of earmarks to support a program that the Pentagon didn't think would work, saying earmarks play a vital role in research and development projects.

“A lot of them fail, but a few of them break through, and the ones that break through prove of great value,” said Hunter, who has served 26 years on the House Armed Services Committee and has sponsored earmarks for duPont and many other San Diego-based defense contractors.

Hunter's support of the DP-2 has thrust him into the center of the debate about earmarks, which congressmen sponsor to fund everything from roads and museums in their districts to defense contracts that can provide hundreds of jobs for constituents.

ABC News reported Monday that duPont provided $36,000 in campaign contributions to Hunter and $18,000 to Christopher Cox, a former Republican congressman from Newport Beach who once worked for duPont and is now chairman of the Securities and Exchange Commission.

Cox now says the project should have been abandoned. “What I supported was doing the testing to determine whether it could fly. As soon as it failed to meet the test criteria, the plane should have been abandoned,” Cox told ABCNews.com.

In an interview before yesterday's hearing, Hunter called the ABC report “a cheap shot” and said the duPont campaign contributions had nothing to do with his support for the program. He noted that he has previously supported cuts for programs of two major contributors: General Dynamics and Lockheed.

“I do what I think is right for the country,” Hunter said.

It was the abuse of the earmarking process that led to the imprisonment of former Rep. Randy “Duke” Cunningham, a onetime House Appropriations Committee member and Rancho Santa Fe Republican who admitted taking more than $2.4 million in bribes in return for directing federal work to defense contractors.

Cunningham is serving an eight-year, four-month term in federal prison after pleading guilty to conspiracy and tax-evasion charges.

Rep. Dana Rohrabacher, a member of the House Science and Technology Committee, also defended earmarks for the aircraft, including two that he sponsored. He also hailed duPont President Tony duPont as “a respected engineer” and “a maverick.”

“When we come to the point where we don't (give) mavericks and free thinkers the chance to prove their theories, we're putting a great limitation on what our potential is for the future, said Rohrabacher, R-Huntington Beach.

Nevertheless, a half-dozen aerospace engineers and other experts who testified before the subcommittee yesterday expressed skepticism that duPont could deliver on its research. They also accused the company of mismanagement.

Air Force Reserve Lt. Col. Michael Tremper, who evaluated the DP-2 program for the Defense Contract Management Agency, said that in 2003 it was found to be deficient “in virtually all evaluated aspects of the operation.”

The consensus of the expert witnesses was that the aircraft was nowhere near delivering on the promises cited by duPont and its congressional supporters.

“It's a pipe dream,” said John Eney, an aerospace engineer who led a Navy team that evaluated the project in 1999.

According to a background report provided by the subcommittee, two separate DP-2 prototypes have “suffered four mishaps” over the last four years. In 2003, during a controlled hover test at Gillespie Field in El Cajon, where duPont keeps the DP-2, the report said the “aircraft had a 'hard landing' and suffered significant damage.”

In a November 2004 test, the plane suffered structure failure “due to engineering deficiencies,” the report said, citing a NASA review. A pilot was in the cockpit at the time – a violation of safety protocols established for the test. As the cabin filled with hot exhaust and composite dust, the pilot was forced to escape through a cabin window because the main door was jammed shut.

The committee report says duPont had plans to make commercial versions of the aircraft and noted that “no ejection seats had been planned or installed for the DP-2, even though it was being developed as a military aircraft.”

Eney yesterday said duPont's plan to give the aircraft the ability to hover like a helicopter by directing jet exhaust toward the ground would incinerate or at least seriously hamper any troops who rappelled out of the aircraft, as depicted in an artist's rendering.

Hunter “failed to understand the basic physics of this situation,” he said.

Tony duPont, testifying from San Diego through a video link, disputed the claim.

He said the jet exhaust would have a low enough temperature that exposure to it would be “like wading in a trout stream.”