In the wake of two deadly crashes in recent weeks involving avid pilots, the Aircraft Owners and Pilots Association (AOPA) has a message for its members: The danger of hypoxia, or a limited oxygen supply to parts of the body, is one that general aviation pilots should take seriously.

On Sept 5, Larry Glazer, the president of the TBM Owners and Pilots Association, died when his aircraft crashed off the coast of Jamaica, after Glazer lost consciousness at the controls. The plane flew for hundreds of miles at high altitudes with two unconscious people on board. It was tailed by F-15 fighter jets for much of the flight.

In a safety alert [PDF] issued over the weekend, AOPA’s Air Safety Institute noted that hypoxia hasn’t been declared the cause of the two accidents, but the likelihood that it was a factor raises concerns that pilots should heed.

“The good news is that [general aviation] pilots have a powerful, low-cost tool available to help avoid succumbing to the effects of hypoxia,” the safety alert states. “A pulse oximeter is the best defense against hypoxia and can be purchased from a variety of aviation vendors or any drug store.”

AOPA recommends that pilots use the device to check their oxygen saturation levels every 10 to 15 minutes in unpressurized aircraft and as needed in pressurized aircraft. Pilots who think they may be experiencing hypoxia (symptoms include headache, hot flashes, and impaired vision) should use supplemental oxygen and contact air traffic controllers on the ground, the association says.