Planes grounded by extreme heat in Phoenix, Arizona

A heatwave is sweeping America's southwest this week, with weather authorities warning residents temperatures could reach as high as 49 degrees Celsius in Phoenix, Arizona.

But while that's bad news if you live there, it's worse if you're trying to get out: More than 40 flights operated by American Eagle – American Airlines' regional service – and scheduled to fly out of Sky Harbor International Airport between 3pm and 6pm local time were cancelled.

American Eagle's parent company explained the decision to temporarily halt service in a press release to USA today, saying the Bombardier CRJ aircraft used on some of American Eagles' shorter routes has a maximum operating temperature of 47 degrees Celcius.

Flights scheduled for the same time on Wednesday and Thursday will also be rescheduled, the company said.

A plane's ability to take off is more severely impacted by hot air than cold air because hot air is thinner, meaning the plane requires greater speed to become airborne. Unfortunately, most runways aren't long enough to accommodate the extra distance the planes would need to reach that speed.

Bigger aircraft, like Airbus or Boeing, can safely take off in hotter conditions, operating in maximum temperatures of 52.7 and 52.2 degrees Celsius respectively.