Learjet 15

Continuing to climb past its allocated height, the plane missed the westbound turn towards Dallas over northern Florida and resumed its northwest course, fleeing almost four hour long and 1,500 mile ( 2,400 km) over the south and central United States. Besides Payne Stewart and three others there were two drivers on board:

Probably the cause of this incident was the inability of the air crews to get additional air pressure in the aircraft cabins due to a pressure drop. Board added a comment on the possible causes why the crews did not get additional oxygen: After pressure relief, no additional air was given to the pilot in enough amount of quality and/or concentrated air to prevent hyperoxia and disability.

Wreck indicated cylinder air cylinder throttle/stop cock was open during casualty flying. Although one masking tube connection of the aircrew was found in the wreck separated from its vent holder (the other connection was not found), the damaged restored connection and both connections agreed that both aircrew masks bolted to the aircraft's air intake pipes at the moment of the collision.

Furthermore, both masking mics of the flying squadron were inserted into the corresponding mic sockets of the team. Under the assumption that the cylinder contains sufficient amounts of air, additional air should have been available for the airframes of the two pilot aircraft. One possible reason for pilots' failing to obtain distress medication is that their capacity to think and act crucially was compromised by high blood pressure before they could put on their breathing apparatus.

There is no clear proof of how quickly the casualty aircraft loses cab air compression, so the Safety Board has assessed the requirements for fast and progressive relief. Had there been a break in the hull (even a small one that could not be seen by the on-board observers) or a gasket leak, the cab could have been slowly, quickly or even explosive depressurised.

The research has shown that a mere 8 second interval without additional air supply after fast relief of air at 9,100 meters (30,000 feet) can cause a decrease in air satiety that can significantly affect one' s ability to cognitively function and prolong the amount of times needed to perform difficult work. Greater decreasing compression could have resulted from other possible causes, such as minor leakage in the tank or a shut-off current regulating device.

The Safety Board's tests showed that a shut-off current regulating solenoid would provide full pressure relief of the aircraft's head for a few moments. Without additional air, however, significant detrimental impacts on one' s mental and locomotor abilities would have been likely soon after the first clear evidence of de-compression (warning of cab height) if cab height had been 3,000 meters (3,000 feet) (which could have happened in about 30 seconds).

Studies of other casualties in which aircraft crew tried to diagnosis a pressure issue or trigger accident pressure application instead of immediately applying air mask after a cab height alarm have shown that even with relatively progressive pressure relief, the pilot quickly loses either his or her ability to cognitively or motorly correct the issue or apply their mask quickly.

An explanation for the crew's omission to receive additional air in good times to prevent incapacity in this case could be a delayed application of air mask in the case of an explosion or fast de-compression of only a few seconds, or a slightly longer delayed application in the case of a progressive de-compression.

NTSB's reports showed that the aircraft underwent several cab pressure-related service operations in the preceding few month period. Sunjet Aviation was criticized by the review for the fact that this would have made it more difficult to detect, trace and solve the issue, and that in at least one case the aircraft was operated with an unwarranted delay in servicing for aircraft pressurization issues.