It's a part of air travel that you don't see. At 30,000 feet, you're surrounded by miles of highly charged electrical wire.
"It's over top of you, underneath the floor, on either side of the aircraft," says air safety advocate Ed Block.
But, now, test videos -- most obtained from the F-A-A's own files -- show how some of that wiring can virtually explode. Another type, if it catches fire, might never stop burning.
"I've never seen it, and I've been involved in aviation safety for 20 years," Block says, watching one of the videos.
But it's a safety issue that, former FAA watchdog Mary Schiavo says, the agency knows full well.
"They know it's a problem, but they hope it won't become a disaster before these planes are phased out of service," says Schiavo, who served as inspector general for the U.S. Department of Transportation.
Take, for example, the MD-80s that American and Delta airlines were recently forced to ground for wiring inspections.
In that case, it wasn't just any type of wire.
It was a wire called Kapton.
"You are going to see an initiation point," Block says, pointing to video of Kapton wire igniting. "And you can see it's burning like sparklers on steroids."
Block, a former Defense Department wiring specialist, set up the test. It shows how the current can jump from a crack in the insulation of one wire to another, with the insulation itself causing a violent flashover.
That flashover is a reaction called "arc tracking."
"It's a chemical reaction of the insulation material -- originally made by duPont, who makes dynamite," Block explains. "It almost looks like dynamite when it's exploding and actually running up the wire bundles in both directions."
And the FAA's own tests show Kapton is more likely than any other wiring to arc track, producing temperatures of 2,000 degrees Fahrenheit.