Between oxygen depletion and the freezing cold temperatures, medical experts say the teenage stowaway from San Jose is lucky to be alive.
One question on many minds is how is this physically possible?
The flight tracker shows the plane reached 38,000 feet. That's higher than the world's tallest mountain.
"It's going to be roughly 10,000...close to 10,000 feet above Mount Everest," said Dr. George Macris with Hawaii's Hyperbaric Treatment Center.
"I was absolutely amazed that this individual survived," he said.
Doctor Macris says those five freezing hours on Hawaiian Airlines Flight 45 could be the reason the teen survived.
The temperatures at that altitude are typically 70-degrees below zero.
"Back in the day when they did open heart surgeries and they did not have heart lung machines, they would actually cool people down a few degrees and they could survive longer with their heart stopped," Dr. Macris said.
Experts say the brain's natural response to extreme cold, essentially shutting the body down, likely kept the boy alive.
Then there's the oxygen level.
At the earth's surface, we breathe about 20-percent oxygen.
Dr. Macris says the boy was breathing about five percent oxygen.
"Five-percent seems to be the absolutely cutoff, at rest, for a limited period of time for survival," he said.
It's unclear if the boy suffered any brain damage, but Dr. Macris says it's certainly possible.
"My guess would be since the brain is extremely sensitive to low oxygen that he could have cognitive impairment which means his processes, his thinking processes could be delayed, his ability to do mathematics, he might behave like somebody who had a stroke."
This story is far from over as a new chapter in the medical field begins.
"This is very fascinating and I think there's going to be...information is going to be learned from this from the tolerance of human survival," he said.
Although the teen is extremely lucky, he isn't the only one.
The Federal Aviation Administration says there have been 105 stowaways since 1947. Of those, 25 have survived.