Your average jet aircraft cruises between 30,000 and 42,000 ft. This is approximate 5 – 7 miles up in the air. The higher the altitude the less dense the air, or put in a different way, the thinner it is. read more
John Cox , Special for USA TODAY Published 6:02 p.m. ET Feb. 2, 2014 | Updated 6:08 p.m. ET Feb. 2, 2014 Commercial aircraft are certified for a maximum altitude, but the limit is exceeded slightly during test flights. read more