Soda Cans Are Exploding Like ‘Little Bombs’ on Southwest Flights. Here’s Why

A routine job for Southwest Airlines flight attendants is turning into a dangerous mess as the scorching summer heat and the airline’s beverage management practices cause soda cans to become unstable in-flight.

There were more than 100 reports of exploding soda cans on flights in June, Bill Bernal, president of the Southwest flight attendant union, told CNN. Some of those cases involved injuries to flight attendants. Bernal predicted nearly three times as many reports of exploding cans by the end of July.

The problem has been going on for “years,” but this year there have been more incidents than usual, he added.

Southwest Airlines declined to comment on the number or nature of the incidents or injuries, but confirmed to CNN that the problem is occurring.

The danger is unique to Southwest because the airline does not serve perishable items and is therefore not required to have refrigerated trucks or storage, CBS News reported. That could expose the cans to extreme heat conditions at several airports in the hottest parts of the country: Las Vegas, Phoenix, Houston and Dallas.

According to Kate Biberdorf, a chemistry professor at the University of Texas at Austin, the cans of carbonated beverages are under such tremendous heat pressure that they resemble “little bombs” that can burst with the slightest movement, even if they are not opened.

“I don’t want to say this to scare people, but that’s how you have to see them,” Biberdorf warned.

“We are aware of the issue and have taken steps to keep beverages cool on board, particularly in our airports where temperatures are extreme,” a Southwest spokesperson said in a written statement.

Extreme heat has been common this year as fossil fuel pollution leads to more frequent and intense heat waves. About 100 U.S. cities are experiencing their hottest summers on record, including southwestern hubs Phoenix and Las Vegas.

Southwest and the union representing flight attendants told CNN they are working together to address the issue.

These efforts include the use of refrigerated supply trucks and trailers to transport and store carbonated beverages and the use of temperature guns to measure cans and determine whether they are safe to load onto an aircraft.

“Both the short-term and long-term solutions are actually engineered solutions that should ultimately almost completely resolve the exploding can problem at Southwest Airlines,” Bernal said.

How Cans Become ‘Little Bombs’

Extreme heat and carbon dioxide do not mix. Even if the problem goes away at Southwest, it could happen anywhere.

The carbonation in soft drinks or sparkling water is created by adding carbon dioxide to a liquid base, mixing and capping.

The carbon dioxide fights to return to its original gaseous state, which is why soda and other carbonated beverages are fizzy. It’s also why carbonated beverages go flat when left open for extended periods of time – all the carbon dioxide gas leaves the liquid and escapes into the air.

When a can of soda is exposed to heat, the carbon dioxide gas in the mixture separates and expands, creating pressure on the can from within, Kate Biberdorf told CNN.

According to Biberdorf, soda cans are designed to withstand pressure levels three to six times higher than the can’s normal pressure.

But if that pressure level is exceeded or if there is a small error in the production of the can, it can become a “little bomb,” Biberdorf explains.

If a Southwest Airlines flight attendant handles or opens a can while serving drinks, with the pressure nearly reaching the point where the can is about to break, the can can easily burst, Biberdorf said.

Altitude probably doesn’t matter, because airplane cabins are pressurized to conditions similar to Earth.

But what happens to Southwest’s cans is the same as what might happen to an unopened can of carbonated beverage left in a hot car.

“In the summer, people keep cans in their cars and that’s usually fine, but once you start driving, there’s a little bit of extra force involved. Maybe the can hits the side (of the car) and explodes,” Biberdorf explains.