More than 18 months after a Learjet accident nearly took the lives of [article id="1595303"]DJ AM and Blink-182's Travis Barker[/article] -- and killed four others -- a federal safety investigation has found that under-inflated tires were the cause of the deadly crash.

According to The Associated Press, the National Transportation Safety Board said the combination of the poorly inflated tires, a design flaw in the Learjet 60 and the decision by the flight's captain to abort takeoff when it was too late contributed to the September 2008 accident in Columbia, South Carolina. The crash took the lives of the jet's pilot and co-pilot as well as Barker's bodyguard, Charles Still, and assistant, [article id="1595413"]Chris Baker[/article].

"This accident didn't have to happen," said NTSB Chair Deborah Hersman, adding that the aviation industry should take notice that there are "no small maintenance items, because every time a plane takes off lives are on the line."

NTSB investigators found that the operators of air charter flights often aren't aware of how quickly the tires of some small business jets can lose pressure and aren't checking inflation levels often enough. It also said the Federal Aviation Administration and Learjet Inc. didn't take aggressive enough action to fix a design flaw in the thrust reversers on the model of jet involved in the crash, which played a role in a similar 2001 accident in Alabama that seriously injured two people.

According to the report, all four tires on the plane exploded seconds apart as it hurtled down the runway on September 19, 2008, with pieces of the shredded tires flying up at high speed and damaging the plane's hydraulic system, causing the brakes to fail. The charter company that operated the plane estimated that the tire pressure had last been checked three weeks before the accident, even though investigators said that the type used on the jet would need to be replaced after eight days if not properly maintained.

A pilot could not tell just by looking at them if the tires were under-inflated and FAA regulations don't allow commercial pilots to use instruments to measure tire pressure.

With only 35 hours of experience flying the Learjet 60 model, the plane's captain made the instant decision to abort takeoff, even though the plane had already passed the speed at which a takeoff could be safely rejected. Additionally, the report noted that damage to an electronic sensor caused the plane's computers to conclude that it was airborne when it was still on the ground, eliminating all chances that the pilot could stop it. That sensor glitch automatically closed the thrust reversers, which can also be used to slow down a plane, and increased the forward power to the engines.

As a result, the plane sped off the runway and crashed through a fence before crossing a five-lane highway and bursting into flames after hitting an embankment. Though engulfed in flames, [article id="1595445"]Barker and AM (born Adam Goldstein), were able to jump out of the plane[/article] before it caught fire, but both were critically burned during the incident. Though AM survived the crash, he [article id="1619854"]died of an accidental drug overdose[/article] less than a year later, in August 2009.

[article id="1627880"]Barker and the families of Still and Baker[/article] have reached legal settlements with several companies over the accident. After amending it to include a wrongful death claim that presumably argued that the injuries the DJ sustained in the crash of the private Learjet had left the former drug addict in so much pain that he had sought relief through various drugs, [article id="1629802"]AM's estate settled[/article] a $20 million lawsuit in January.