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Record-breaking temperatures in Southwest ground flights

Extreme temperatures in the southwest of the United States and an unusual week-long heat wave are grounding flights. As temperatures in some areas hit 48°C, the heat becomes a particular problem for some commercial airliners with that maximum operating temperature, Wired reports. The reasoning behind this lies in the so-called momentum principle: High temperatures decrease the air’s density, preventing the lift necessary for planes to take off. 

*Update, 22 June, 4:18 p.m.: A previous version of this story referred to the “monument principle.” This has been corrected to the “momentum principle.”

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