Boiling Point of Water in an Airplane

Why does water on a commercial jet flying at standard cruising altitude (about 35,000 feet)boil at 89 degrees centigrade? If the cabin is pressurized, shouldn't the water boil at 100 degrees C.?
- Adam (age 50)
Beverly,MA

That is a very good question. The reason why water boils under 100 degrees Centigrade or 100 degrees Celsius is because commercial airplanes are not pressurized to air pressure at sea level, but to about 8,000 feet or about 2,400 meters. At this effective altitude, water boils around 91.6 degrees Centigrade. As an interesting fact, one of the reasons Boeing advertises flying on the 787 Dreamliner is because it will be pressurized to about 6,000 feet or about 1,800 meters. At that effective altitude, water will boil at around 93.6 degrees Centigrade.

Erik

For those who would like to know how pressure is related to boiling point, look . For those who would like a more mathematical equation relating pressure and boiling point, look .

(published on 01/30/2013)