In 1999 a private jet en route to Dallas, Texas alerted Air Traffic Controllers when
it stopped responding to radio transmission and began deviating from its intended course.
Fearing something was amiss, fighter jets were scrambled to intercept it, but when they
caught up with the craft, it didn't seem to be in any distress.
However, there was no reaction to the presence of the fighters, and their pilots noted there
didn't seem to be any movement in the cabin or cockpit.
So, what was happening to the aircraft?
And what was going to be done about it?
In 1999, PGA golfer Payne Stewart had won the US Open.
A few months later, he was headed to Houston, Texas for the year-ending tournament, the
Tour Championship.
He decided he would stop in Dallas first, however, for discussions with the university
he attended about building a new course for the school's golf program.
On October 25, 1999, Stewart set out from his Orlando home to Dallas in a Learjet Model
35.
He was accompanied by a group of three consisting of his agents and a golf course designer.
The craft was piloted by 42-year-old Michael Kling, an airline transport pilot with Air
Force experience flying KC-135 Stratotankers and Boeing E-3 Sentries.
He was also a flight instructor in the Maine Air National Guard.
His first officer was 27-year-old Stephanie Bellegarrigue - a commercial pilot who was
also a certified flight instructor.
They departed Orlando International Airport at about 20 past 9 in the morning, with four
to five hours worth of fuel on board - more than enough for the 2.5 hour trip to Dallas.
About ten minutes after takeoff, air traffic control instructed the pilot to climb to 39,000ft
(11,900 m) and maintain level flight at this altitude.
The pilot acknowledged the controllers' request and began to climb, it would be the last time
they would hear his voice.
Six minutes later, the controller tried to contact the Learjet again, but there was no
response.
Odd, as they had just spoken.
Over the next four minutes the controller tried to contact the pilot five more times,
each time with no response.
Air Traffic Control now pondered what was causing this radio silence - was it malfunction,
or was there a hijacking?
At nearly 10am, this information was passed along to US Air Force Base in western Florida.
An F-16 test pilot happened to be in the air at the time, and he was instructed to intercept
the Learjet.
When he caught up with it he noted it the aircraft didn't seem to be undergoing any
struggle to stay aloft, although, it was still slowly climbing past its instructed altitude,
and it appeared the craft was headed North instead of turning West to Dallas.
The fighter pilot made two radio calls to the Learjet - no response.
He went in for a visual inspection of the craft, but couldn't see any signs of damage,
and both engines were running.
The signs seemed to point more towards hijacking than malfunction.
The pilot tried to peer through the Learjet's windows and into the cabin, but couldn't see
anything - perhaps the cabin was too dark.
He moved to have a look at the cockpit.
He couldn't see much through the cockpit windshield either, although now he understood why.
The windows were frosted over.
He couldn't see any shadows moving behind the frost, it seemed the cockpit was completely
still.
Within 15 minutes the fighter pilot had completed his inspection, he broke formation and left
the Learjet.
The Learjet continued its new path North.
It continued to climb to an altitude of nearly 50,000ft (48,900 feet (14,900 m)).
This continued for hours, as there was little anyone could do except send fighter jets to
intercept the craft.
Two more interceptions occurred, although they had no more success than the first.
As the craft headed further and further North, the Canadian Prime Minister (Jean Chrétien)
was informed if it continued, it was headed towards Winnipeg.
The Prime Minister said that if the Learjet crossed into Canadian airspace without making
radio contact, the military had permission to shoot it down.
Nearly four hours into its journey, the Learjet had flown 1,500 miles (2,400 km) across the
United States, and was passing over South Dakota.
By this point, the fuel was running out.
F-16's following along side the craft watched its nose sink downwards, and the plane entered
a drastic spiral.
They lost sight of it through the clouds, and by the time they re-established visual
contact, it was a burning wreckage on the ground.
The Learjet had nosedived at near supersonic speed, leaving no chance of survival for any
of the six on board.
Thankfully, it crashed in sparsely populated farmland.
The National Transportation Safety Board began an investigation of the highest priority,
owing to the mysterious circumstances surrounding the crash.
There was no flight data recorder on board the Learjet, although they did manage to recover
the cockpit voice recorder, or CVR.
Even this yeilded little information, as the CVR was an older model and held only the last
thirty minutes of audio, during which nothing is heard from the cockpit except for the plane
itself - the autopilot can be heard disengaging after the fuel ran out and the Learjet began
to stall.
It was ruled that the most likely explanation for the crash, was that the Learjet experienced
decompression of the cabin.
How exactly this occured is unknown, but it would explain a number of things.
Firstly, the frosted windows.
If the cabin lost pressure at such a high altitude, it would experience a significant
decrease in temperature and humidity.
This rapid cooling can cause condensation to form on surfaces, including windows, and
is a common occurrence during decompression events.
It is unknown if the decompression was gradual, rapid or even explosive.
Regardless, the loss of pressure would have hindered the process of oxygen exchange that
occurs in the lungs, leaving those on board suffering from hypoxia, a lack of oxygen to
the body and brain.
It was found the oxygen mask system on the Learjet was more than likely fully operational
during the incident, but just a few seconds of hypoxia is enough to effect cognitive ability
and motor skills.
Under hypoxia's influence, the crew likely didn't have the sense or the physical co-ordination
to apply the oxygen masks.
Without a supply of oxygen, they'd be rendered unconscious shortly after.
This would explain the lack of response from the craft so soon after its last transmission.
Everyone on board was incapacitated.
If this version of events is accurate, the six on board would have died of oxygen starvation
long before the plane crashed, meaning the autopilot had carried a crew of the dead for
hours.
Certainly an eerie scenario, but as plane crashes go, it was perhaps one of the most
peaceful ways you could hope to spend your last moments.