American Airlines alerted customers over the weekend that over 40 American Eagle flights scheduled to depart from or arrive in Phoenix between 3 p.m. and 6 p.m. local time on Monday and Tuesday afternoon - during peak temperatures - would be cancelled, allowing customers the option to request a refund or change travel plans for no additional fee.
The Western United States is bracing for more record heat with temperatures expected to hit 110 to 120 degrees on Tuesday in some places. Out-of-town visitors tried to stay inside air-conditioned casinos as much as possible, and some tourists lugged packs of bottled water around the Strip.
In Phoenix, hundreds flocked to Grace Lutheran Church for water and refuge.
That is what American Airlines did during the recent Phoenix heat wave.
"We have homeless people come from a long way to sit here", longtime volunteer Moses Elder said.
Phoenix has been on watch for 120 degrees (49 degrees Celsius) for several days, a mark only reached three times in recorded history. The study of almost 2,000 deadly heat waves worldwide since 1980 was published Monday in the journal Nature Climate Change.
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Hot air, which is less dense and more excited, forces the plane to build more speed before it can take off.
It's so hot in the city on Tuesday, that American Airlines cancelled almost 50 flights, due to the heat exceeding the safety limits of some of their jets.
The National Weather Service is telling residents to take the heat seriously, with a somber warning on its website: "If you don't take precautions immediately when conditions are extreme, you may become seriously ill or even die".
Shelby Barnes, 48, picked up three sets of the booties for her dogs.
"If you can't put your foot on the sidewalk, neither can they", she said. This current heat wave looks like it'll bring the fourth-hottest day on record for America's hottest city.
The county that is home to Phoenix had 130 heat-related deaths in 2016, the highest number in more than a decade.
Airplanes take off and stay in the air because of lift - the force from the movement of air under the plane's wings that push it upward.
At McCarran International Airport in Las Vegas, airlines cancelled at least one flight and delayed at least two others because of the heat.
Excessive heat is not uncommon from June to September, though National Weather Service meteorologist Kate Guillet said the early part of summer can be slighter hotter as the region awaits monsoon season.