User: How many miles up.do airplanes fly

Note: How many miles up does an airplane go? Large jets such as Boeing 747 cruise at about ... [ How many miles up do airplanes fly www.answerbag.com/q_view/967689 ]
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Weegy: Cruising altitude (which can vary depending on weather) for commercial flights is about 12,000 meters, or 7 miles in the air.
Expert answered|topshi|Points 1911|

User: When does the air become too thin

Weegy: A cubic metre of air at sea level contains about 1.2 kilograms of air. Higher in the atmosphere, a cubic metre would contain less air. [ For example, at 9,000 metres (the summit of Mount Everest) a cubic metre of air would contain only about 0.47 kilograms of air, less than half as much as at sea level. It is this decrease of mass per unit volume (density) that I mean when I write of the air getting "thinner". http://bencraven.org.uk/atmosphere.html ]
Expert answered|jeifunk|Points 5142|