( CNN ) -- The pilot or pilots aboard an unresponsive plane that flew from the United States over the Caribbean Sea on Friday may have been stricken by cerebral hypoxia -- a fancy term for when your brain is deprived of oxygen . The North American Aerospace Defense Command ( NORAD ) scrambled fighter jets to check on the plane and suggested on Twitter that hypoxia may be to blame . Before the small plane 's windows frosted , fighter pilots tracking the plane could see a pilot slumped over , a NORAD official said . Cerebral hypoxia can happen to pilots if they reach too high of an altitude or if there is a loss in cabin pressure . It can also be the result of carbon monoxide poisoning or breathing in too much smoke from a fire . There is a progressive reduction of oxygen per breath the higher the altitude . Every pilot 's reaction to hypoxia is different , according to a the Federal Aviation Administration . But is extremely hard for a person to tell when it is happening to them because the onset of symptoms is subtle . In the beginning , pilots may experience an increase in the rate at which they breathe . They also may feel lightheaded or dizzy . Eventually , they will start to lose coordination . They will experience tunnel vision and their judgment would become impaired . Brain cells are particularly vulnerable to a lack of oxygen . Without it they can die off and cause permanent brain damage . When a brain goes without oxygen for too long , the part of the brain that helps with breathing can stop working and can keep you from breathing . Federal investigators believe golfer Payne Stewart 's Learjet went down in 1999 after his plane lost cabin pressure during its flight . In that case , a low-pressure alarm could be heard on the cockpit voice recorder recovered from the wreckage . The FAA said his plane climbed as high as 51,000 feet . The human body has limited ability to function above 10,000 feet without additional oxygen .
Cerebral hypoxia can be caused by flying at too high an altitude . It can cause someone to pass out , stop breathing temporarily or die . Comment: