A summer heat wave canceled dozens of American Airlines flights out of Phoenix Sky Harbor Airport last year.

The company’s smaller Bombardier CRJ700 and CRJ900 jets weren’t cleared to fly in temperatures above 117.86 degrees. That’s different now, according to an American Airlines press release. 

The same planes are now ready for take-off in temperatures up to 123.8 degrees.

“There’s actually no physical modification," said Ross Feinstein, a spokesman for American Airlines. "What it really is obviously doing [is] a study to make sure the aircraft can perform at that temperature.”  

The company worked with Bombardier, the Federal Aviation Administration and regional partners Mesa and SkyWest Airlines over 10 months to modify the maximum operating temperature. 

“Really what it comes down to is science,” Feinstein said. “Obviously, the hotter the air temperature is, the thinner the air, the less lift an individual aircraft will get when it takes off.” 

Hot air is less dense, and planes need to change other factors like weight or speed to take off. The altitude of Sky Harbor is also a factor. 

“We never want to cancel flights due to a weather issue,” Feinstein said.

He doesn’t anticipate the airline will have to ground any flights for heat this summer.