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by Jason Snell & Dan Moren

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Linked by Jason Snell

Why airplanes can’t take off in extreme heat (updated)

I’m flying to Phoenix on Friday. The forecast high that day is 112°F (44C), which is a cooling trend. The last couple of days it’s been nearly 120°F (49C) in Phoenix.

So, funny story: Airplanes are really bad at taking off when it’s really hot. Rhett Allain explains at Wired why hotter air means lower air density, which means less lift, which means that smaller jets can’t take off when it gets to 120°F. I do like a good science story.

Good news, though: The day I’m scheduled to come back home from Phoenix, it’s only going to get up to 110°F. My Southwest Airlines Boeing 737 will probably not have any trouble.

Update

Turns out that among my readership are airline pilots and consultants! I will keep their comments anonymous, but to summarize:

Jet manufacturers certify their aircraft to a given maximum operating temperature as part of the standard delivery package for their aircraft. Airlines cannot operate those aircraft above that limiting temperature. If an airline wants to spend some extra money to get a jet off the ground on a very hot day, they can buy additional performance data and use it to approve take-offs. If you don’t have the data, the FAA doesn’t allow you to take off.

Smaller regional jets don’t necessarily have access to the data for their planes, which is why some stories refer to Boeing and Airbus jets taking off when smaller jets are grounded. Then again, cancelling a small jet with 50 passengers costs a lot less money than cancelling a large jet with nearly 200.