In June, blazing temperatures in Arizona grounded dozens of flights to and from Phoenix. It wasn't because tires were melting, or fuel was overheating. Planes, specifically Bombardier CRJ airliners, couldn't physically lift off the ground at 118 degrees Fahrenheit. (We'll get to why later.)
Coincidentally, a new study, published today in the journal Climatic Change, asks a similar question: Based on extreme climate change scenarios (think worst-case) predicting what future temperatures might be, could planes safely take off in record-high heat?
I'm going to say, right off the bat, that even the most nightmarish climate modeling didn't signal catastrophic results for flying, according to the study. But there could still be not-insignificant consequences for airplane design and airport infrastructure, not to mention passengers being booted from flights.
The team used historical and projected yearly maximum temperature trends to predict daily temperatures at 19 major global airports—such as Denver International Airport, and Dubai International Airport—as far into the future as the year 2080. Then, using publicly available aircraft performance data, they calculated how air temperature would impact a jet's maximum takeoff weight, factoring in variables like runway length and airport elevation.
This was done for five commercial aircraft: the Boeing 737-800, Airbus A320, Boeing 787-8, Boeing 777-300, and Airbus A380.
Takeoff weight was the crux of the study, since hotter temperatures can decrease air density, which means less lift for departing planes. This is why certain aircraft were grounded in Phoenix last month. Pilots can generate more lift by increasing the plane's speed, but not if the runway isn't long enough to accelerate.
So how do you make a plane lighter? By removing fuel and passenger loads, said the authors. In the future, on average, 10 to 30 percent "of annual flights departing at the time of daily maximum temperature may require some weight restriction below their maximum takeoff weights," they wrote. This is something that's already being done on hotter days at places like London City Airport.
Mean weight reductions could range from 0.5 to four percent, the study claimed. On a Boeing 737-800, this would mean bumping approximately three (likely furious) passengers to another flight. For planes that seat 160 people, this would mean a whopping 12 or 13 passengers. Some planes could fare worse than others, depending on an airport's runway and elevation, the study noted.
At LaGuardia Airport in New York, which has shorter runways (7,000 feet), a Boeing 737-800 would need to reduce its weight by half for all departures on the hottest days, cutting 3.5 percent of its fuel and passenger load. Dubai International Airport has longer runways (14,590 feet), but even so, a Boeing 777-300 would need to offload 55 percent of the time, eliminating up to 6.5 percent of its fuel and passenger load.
The study's authors used various emissions models from the Intergovernmental Panel on Climate Change, basing their predictions on medium- to worst-case climate scenarios.
I contacted the authors about why they used these exact models for their study, but did not receive a response by deadline.
The study also mentions, but doesn't explore in great detail, the economic and social side-effects of all this. Backups at major hubs could ricochet around the world. And passengers may begin to avoid airports where temperature-related delays are common. Weight restrictions likely pose a "non-trivial cost" to airlines, according to the authors' conclusion.
More probably, the threat of rising global temperatures will spur technological improvements to aircraft efficiency, like better engine performance. Or, airports may begin to lengthen their runways, though the process of doing that can be difficult. In places like Phoenix, air traffic controllers are already rescheduling flights to cooler hours of the day.
"The sooner climate can be incorporated into mid- and long-range plans," said lead author Ethan Coffel in a statement, "the more effective adaptation efforts can be."
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