On Monday, July 8, 1940, the first commercial flight using a pressurized cabin took place on a Boeing 307 Stratoliner, flying at an altitude of 20,000 feet from New York to Burbank, California. Pressurization is essential over 10,000 feet above sea level to protect crew and passengers from the risk of a number of physiological problems caused by the low outside air pressure above that altitude; it also serves to generally increase passenger comfort. For passenger comfort, cabin pressure is changed to match the destination altitude as the flight descends for landing. Above: one of only ten Boeing 307s manufactured – later, Boeing built the bigger and better Stratocruiser.
