SAN DIEGO -- The next time you fly, the airplane you board may have been repaired by someone who isn't a certified airline mechanic, according to 10News.

More and more, airlines are outsourcing maintenance, 10News reported.

Experienced airline mechanics said sending repair work to third-party shops is like playing Russian roulette with a jet. They added that several crashes have already prove their point.

In 1996, a Value Jet plane crashed into the Florida Everglades and killed 110 people. In 2000, 113 died in the Concorde crash in France. And, 21 more people were killed when an Air Midwest commuter plane crashed last year.

What do these disasters have in common? According to Ken Mactiernan, from the Aircraft Maintenance Technicians Association, outsourced maintenance played a part in all of the accidents.

"The public may be in danger in the future as the airlines make a mad dash to outsource as much work as they can get away with," Mactiernan said.

According to the Department of Transportation, the country's 13 largest airlines are outsourcing huge portions of their mechanic work.

Overall, airlines in the United States send about one-third of their work to outside repair shops. In fact, America West, Alaska and Southwest airlines all outsource more than half of their work to other companies.

So, what's the problem with outsourcing? Airline mechanics who are trying to stop the trend said work is not getting done or is done poorly, and passengers are at risk.

Former United Airlines mechanic Tim Hafer supplied 10News' investigative team with documents showing secretaries, not mechanics, signed off on outsourced repair jobs.

"It looks like it was never even done. I mean, the fact that the (Federal Aviation Administration) inspector told me United (Airlines) couldn't come up with written paper work, that basically (tells me) the work was never done," Hafer said.

Hafer said he was fired after reporting the violations to the FAA.

The 10News investigative team also uncovered photos of shoddy work done at outside maintenance centers, including:

wires damaged and left on a 757
a fuel leak that was improperly repaired
a 747 jet engine that came apart in flight after an overhaul
missing bolts and nuts from a 737 door, which was discovered just before takeoff

"Airplanes are very forgiving. I mean, you can beat an airplane and it will forgive you only so many times," Hafer said.

The quality of outsourced repair work in the United States is not the only concern. Critics are also troubled by what they say is a lack of security in overseas shops.

"I don't think it would be very difficult at all. I mean there are a lot of places on a plane where you can hide or do whatever you want to do," Hafer said.

"I can assure you that the Transportation Security Administration, along with DHS and its partners, has processes in place to address those (concerns). We are continually looking for those gaps and seams that somebody would use to get inside our security apparatus," said Mike Aguilar, a federal security director, about Hafer's allegations.

The bottom line is that airlines say outsourcing lowers costs and airfares, but the mechanics 10News interviewed said saving $100 on a flight could cost a passenger their life.

"In the most extreme case, they can put that $100 toward a coffin," Hafer said.

Certified airline mechanics will picket against outsourcing maintenance jobs for three days next week in Washington, D.C.

Southwest Airlines said it keeps a close eye on the quality of its outsourced work. Spokesperson Angela Vargo said passenger safety is the first concern, and all repair work goes to the original manufacturer or a specialized vendor. Southwest has not had a fatal crash in its 33-year history.

But, 10News' sources said it is only a matter of time before the lack of experience at outside repair shops leads to another crash and more deaths.

Responses To Recent Media Reports On Maintenance Outsourcing:

Air Transport Association's Response
Southwest Airlines Response