The reason small planes cannot take off when it's too hot

Hot weather causes the air to dilute, reducing the lift, making small aircraft unable to take off.

Dozens of flights in the western United States were canceled this week and many other flights were at risk of being unable to take off because temperatures reached a record high of nearly 50 degrees Celsius.

On hot days, the air density is the obstacle of pilots controlling small aircraft to take off, according to the AP. The heated air becomes thinner, causing most small aircraft to lack lift to safely take off.

If trying to fly, the aircraft may not be able to leave the runway or cross the runway if it tries to land.

The aircraft can take off thanks to the lift generated by the movement of the air stream below."The air that relaxes when warming makes less gas molecules below the wing," explains Lou McNally, applied meteorology professor at Embry-Riddle Aviation University.

As the lift of the air decreases, the aircraft needs additional from all sources: larger thrust, longer run on the runway with greater velocity. When these requirements exceed the threshold, the operation of small aircraft is paralyzed. If trying to fly, the aircraft may not be able to leave the runway or cross the runway if it tries to land.

In areas with frequent hot weather such as Dubai International Airport and other Gulf airports, many flights choose to arrive at night and early in the morning. Gulf aircraft also tend to make longer flights, using larger aircraft with wider wings so as not to be affected by high temperatures.

Under very high temperatures, airlines sell fewer tickets, reduce cargo or take off with unburnt fuel tanks. The aircraft can choose a cooler point to supply later.

Apart from the main problem, high density air can also weaken or melt connections on aircraft, threatening the safety of passengers and crew, according to Professor R. John Hansman of Department of Aviation and Space at Massachusetts Institute of Technology.