October 26, 1999
Web posted at: 7:27 a.m. EDT (1127 GMT)

From staff and wire reports

ATLANTA (CNN) -- The bizarre nature of Monday's deadly plane crash prompted immediate speculation about its cause.

Early theories from those familiar with the type of Learjet 35 aircraft involved were based on observations by U.S. Air Force pilots who reported that the plane appeared to have lost cabin pressure.

If that had happened, at high altitude, experts say there would have been little time for recovery.

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"You have about 20 seconds to get your oxygen mask on or you'll be incapacitated," said Wayne Sadler, a pilot.

"You'd get a horn, a light would come on, you would automatically go into emergency pressurization and at some point, at 14,000 feet, a mask would automatically drop for the passengers," Sadler said.

Loss of cabin pressure and the loss of access to breathable oxygen eventually will lead to a condition known by physicians as "hypoxic hypoxia."

That's what happens when there are not enough oxygen molecules available at sufficient pressure to supply one's respiratory system.

Symptoms of hypoxia include: increased breathing rate, lightheadedness, dizziness, a tingling or warm sensation, sweating, reduced field of vision and sleepiness.

It can happen suddenly, as occurs at high altitudes during a rapid decompression, or gradually, as occurs at lower altitudes when there is insufficient oxygen available.

The higher the altitude, the less oxygen there is available - - and the faster one can lose "useful consciousness." Without sufficient oxygen, even the simplest tasks -- such as talking on the radio -- may become impossible to complete.

The Learjet 35 carrying golf champion Payne Stewart, other passengers and crewmembers, was reportedly flying at 39,000 feet -- an appropriate altitude for its intended route.

FAA rules require pilots flying above 35,000 feet in a pressurized craft to have oxygen masks that can be placed on the face with one hand in 5 seconds.

The Learjet was among the first small, private jets ever developed. Experts said it has a long, trouble free record with no apparent history of cabin-pressure loss.

According to aviation industry sources, the best information about what went wrong aboard Stewart's private jet may come from toxicology tests that likely will be performed on the crash victims.

Test results may hold clues as to why passengers and crewmembers became too incapacitated to save themselves.