The 55-year old seaplane used to market the Red Bull energy drink at major sporting events and air shows was decommissioned and disposed of by the Coast Guard in 1976 because they considered it no longer safe to fly given the age of its wings.
But it flies over the heads of hundreds of thousands of people a year under an "experimental airworthiness certificate" granted by the FAA in 2008.
In a written response to questions, a Red Bull spokesperson, Patrice Radden, said: "Neither Red Bull nor any of its pilots or flight crews have or would operate an aircraft that is known to be unsafe or in an unsafe manner."
The aircraft is a Grumman-built HU-16E "Flying Albatross."
NFL Star Reggie Bush is Red Bull Spokesperson
New Orleans Saints football star Reggie Bush, a Red Bull paid spokesperson, was filmed flying the plane in the left pilot's seat, climbing into the plexi-glass nose of the aircraft and sticking his head out of an open window.
"I stuck my head out the window which never in a million years I thought I would be able to do," Bush says on a Red Bull promotional video posted on the company's website.
Earlier this month, the Red Bull plane flew over thousands of college students on spring break at Lake Havasu, Arizona.
A spokesman for the FAA said the agency was "comfortable" with the use of the airplane, even if it is flying over the heads of thousands of people a year.
Red Bull says the plane is operated in full compliance with FAA regulations.
"It's terribly unsafe because the wing could fall off at any time," said Bill McNease, a former FAA safety inspector who helped initiate an earlier investigation of the plane when he was with the FAA in 2006.
"The long wing versions of this airplane have a definite, if you want to call it, drop dead time. When they reach a certain amount of flight hours, that's it," said McNease in an interview with ABC News Chief Investigative Correspondent Brian Ross for Good Morning America.
Similar Seaplane Crashed in 2005, Killing 20
The FAA investigation of the Red Bull plane followed the 2005 crash of a similar seaplane, operated by Chalks Ocean Airways in Miami.
Twenty people were killed when the plane's right wing separated on take-off.
"There's the possibility that the same thing could happen" with the Red Bull plane, said McNease.
The FAA investigation relied on a confidential U.S. Coast guard report, obtained by ABC News.
The Coast Guard said it had stopped using the plane in 1976 because "all available service life appears to have been expended."
Total Flight Time Rolled Back
As of 1971, Coast Guard records show, the plane had logged 8,068 flight hours.
Yet in an application for an FAA airworthiness certificate 37 years later, in 2008, the owners of the plane who lease it to Red Bull claimed the plane had only 7,100 hours.
Somehow, the total flight time had been rolled back 968 hours, tantamount to rolling back the odometer on a used car.
"You can't roll back hours," said former FAA inspector McNease.
The Red Bull spokesperson said the plane's owners relied on data it received when it bought the plane in 2000.
The plane's pilot, Lynn Hunt, refused to speak with ABC News about the plane's safety, saying, "I was told to tell you no comment."
In its written response to questions, Radden, the Red Bull spokesperson said it was "a misconception" that the plane had a "definitive life limit."
Radden did not directly answer the discrepancy in flight hours but called the official Coast Guard records "inconclusive and incomplete."
The FAA had actually grounded the plane in 2007 after the discovering of the flight hour discrepancy but relented after the plane's owners hired a Washington law and lobbying firm to protest.
Instead, the FAA issued the "experimental" airworthiness certificate, apparently giving some consideration to the economic plight of the owner, John Shoffner of Flight Management Resources.
"We hope this solution will allow Mr. Shoffner to realize some, albeit limited, economic value for his airplane," wrote Carol Giles, the assistant Deputy Director of Flight Standards Service at the FAA.
Red Bull Plane Flies Over Venues at Major Cities
In addition to the restrictions of flights over heavily populated areas, the FAA said "no person may be carried in this aircraft during flight unless that person is essential to the purpose of the flight."
Red Bull said it strictly follows the FAA restrictions and "does not fly unauthorized people on the aircraft."
Red Bull said that under the terms of its FAA certificate it is permitted to "carry passengers from time to time."
Red Bull says its plane flies over big cities and events with large crowds, including the Super Bowl festivities, "under the direct authority of the FAA and by direction of air traffic control."
Last year the plane flew over 15 air shows and sports events including heavily-attended venues in suburban Washington, D.C., Detroit, San Francisco, Seattle, San Diego and Las Vegas.
Eric Longabardi is a freelance journalist who is a frequent contributor to the ABCNews.com investigative page.
This post has been updated.