This month, Norwegian Air Shuttle will resume its seasonal service between Las Vegas and four European cities. The airline suspended the flights in March because excessive heat had caused it to regularly delay flights out of McCarran International Airport the previous summer. Norwegian Air wasn’t alone. The Las Vegas Review-Journal reported in August that dozens of flights from Vegas were delayed or cancelled during this summer’s record-breaking heat.
Why does heat cause flights to be cancelled? No, it’s not because the tarmac is melting. It has to do with plane weight and air density. “As air temperatures rise at constant pressure, air density declines, resulting in less lift generation by an aircraft wing at a given airspeed, and potentially imposing a weight restriction on departing aircraft,” wrote the team of researchers behind the article “The impacts of rising temperatures on aircraft takeoff performance” in the September issue of the journal Climatic Change.
The solutions? Lighter loads, longer runways (to build greater speed), or more departures during cooler hours. The latter solution was chosen by Hainan Airlines, which moved its two nonstop Las Vegas-Beijing flights from 2 p.m. to 1 a.m.
Others may be forced to follow suit. The Climatic Change study predicts that, by the middle to end of this century, an average of 10-30 percent of annual flights departing at the hottest time of day will have to be lighter in order to take off.