Charles Rex Arbogast/AP
A Southwest Airlines Boeing 737 MAX 8 aircraft flies over the central United States from Tulsa, Oklahoma to Chicago on June 15, 2024.
CNN
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A routine job for Southwest Airlines flight attendants is turning into a dangerous situation due to a scorching summer and the airline’s beverage management practices that have turned soda cans into a volatile substance mid-flight.
Bill Bernal, president of Southwest’s flight attendants union, told CNN that there were more than 100 reports of exploding soda cans on planes in June, including some that injured flight attendants, and that he expects reports of exploding cans to nearly triple by the end of July.
The problem has been going on for “years,” but there have been more incidents this year than usual, he added.
Southwest Airlines would not comment on the incident or the number or nature of injuries, but confirmed to CNN that there were problems.
The risk is unique to Southwest, which doesn’t sell perishable food and therefore doesn’t need refrigerated trucks or storage. CBS News reported.This can potentially expose the cans to extreme heat conditions at airports in some of the hottest areas of the country, including Las Vegas, Phoenix, Houston and Dallas.
Soda cans are like “little bombs” that are under so much thermal pressure they can explode with the slightest movement, even if the can is unopened, said Kate Biberdorff, a chemistry professor at the University of Texas at Austin.
“I don’t say that to scare people, but you really should think of them that way,” Biberdorff warned.
“We are aware of this issue and are taking steps to keep beverages cold on board, especially at airports exposed to extreme temperatures,” a Southwest Airlines spokesman said in a written statement.
Fossil fuel pollution has led to more frequent and intense heat waves, and we’ve seen some extremely hot weather this year. 100 US cities Cities across the Southwest, including the hubs of Phoenix and Las Vegas, experienced their hottest summer ever.
Southwest Airlines and the union representing its flight attendants told CNN they are working together on efforts to mitigate the problem.
Those efforts include using refrigerated supply trucks and trailers to transport and store soda, and using thermometers to measure the temperature of cans to determine whether they are safe to load on aircraft.
“The short-term and long-term solutions are actually engineered solutions that should ultimately largely eradicate Southwest’s can-exploding problem,” Bernal said.
Extreme heat and carbon dioxide don’t mix well, and while this didn’t happen on Southwest Airlines, it could happen anywhere.
Carbonation of soda or carbonated water occurs when carbon dioxide gas is added to a liquid base, mixed and sealed.
Carbon dioxide wants to go back into its original gas state, which is why soda and other carbonated drinks have a fizz, and why carbonated drinks lose their carbonation if they’re left open for too long, because all the carbon dioxide gas escapes from the liquid into the air.
When a can of soda is exposed to heat, the carbon dioxide gas in the mixture separates and expands, putting pressure on the can from the inside, Kate Beberdorf told CNN.
Soda cans are designed and built to withstand pressure levels that are three to six times the normal pressure for a can, Beberdorf said.
But if that pressure level is exceeded, or if there is a small defect in the manufacturing of the can, it can become a “little bomb,” Biberdorff explained.
Biberdorff said if a Southwest flight attendant handled or opened a can that was literally under pressure near the bursting point during beverage service, the can could easily burst.
Aircraft cabins are pressurized to match conditions on the Earth’s surface, so altitude is probably not a factor.
But what happened to the Southwest Airlines can is the same thing that could happen to an unopened soda can left in a hot car.
“In the summer, people will store the cans in their cars and it’s usually fine, but as soon as they start moving, there’s a little bit of extra force and the can hits the side of the car and explodes,” Biberdorff explained.
