Southwest Airlines will soon require passengers to keep their portable chargers visible while using them on flights due to concerns over the increasing number of lithium-ion battery fires—a policy that other airlines might also adopt.

This new regulation, announced by Southwest, goes into effect on May 28. Passengers might have already noticed notifications about this rule when using the airline’s app. Although Southwest is the first U.S. airline to implement such a restriction on portable chargers, some Asian airlines began enacting similar policies earlier this year after a severe fire broke out on an Air Busan plane waiting to take off from an airport in South Korea in January.

Concerns about lithium-ion battery fires on planes are rising as the number of incidents grows annually, with such battery-powered devices being commonplace. This year alone has seen 19 incidents, following last year’s record of 89, according to data from the Federal Aviation Administration.

The incidents have more than doubled since the pandemic-era low of 39 in 2020, and have climbed annually.

Some research suggests that portable chargers might be the second-leading cause of battery fires on planes, only behind electronic cigarettes.

Compared to the roughly 180,000 flights U.S. airlines operate each week, the number of incidents is still relatively small and lithium batteries can overheat anywhere. However, this is a growing concern for the airlines.

“It’s definitely a serious risk,” said David Wroth, who studies the risks for UL Standards & Engagement and works with 37 airlines and battery manufacturers to minimize them. At least a couple of airlines UL is working with are reevaluating the risks associated with rechargeable batteries, so additional rule changes could be coming.

What has happened before?

In the Korean airline fire in January, all 176 people aboard the plane had to be evacuated because the blaze burned through the plane’s roof. The cause of that fire hasn’t been officially determined, but several airlines and Korean regulators took action against portable chargers afterward.

Korean airlines won’t allow the chargers to be stored in overhead bins anymore; they must either be packed in a plastic bag or have their ports covered with insulating tape to keep them from touching metal.

In addition, Singapore Airlines and Thai Airways both prohibit the use or charging of portable power banks at all during flights.

Last summer, a smoking laptop in a passenger’s bag led to the evacuation of a plane awaiting takeoff at San Francisco International Airport. In 2023, a flight from Dallas to Orlando, Florida, made an emergency landing in Jacksonville, Florida, after a battery caught fire in an overhead bin.

Why make this change?

Southwest said that requiring these chargers to be kept out in the open when they are being used will help because “in the rare event a lithium battery overheats or catches fire, quick access is critical and keeping power banks in plain sight allow for faster intervention and helps protect everyone onboard.”

Experts have long recommended keeping rechargeable devices in reach during flights so they can be monitored for any signs of problems like becoming too hot to touch or starting to bulge or smoke. But the airlines have to rely on educating consumers and encouraging them to take precautions.

“Ultimately, it comes down to a lot of personal responsibility that we as passengers have to take,” Wroth said.

Southwest will allow the chargers to be stored inside carry-on bags when they aren’t in use. But a spokeswoman said the airline is just alerting customers about the policy before their flight and asking for their compliance. Wroth said that approach is probably best.

“We have enough problems with unruly passengers already. And having cabin crew confront somebody over bringing something on board is not likely to be a good situation as well,” Wroth said.

What do the existing rules say?

The Transportation Security Administration has long prohibited e-cigarettes and chargers and power banks with lithium-ion batteries in checked bags, but allows them in carry-on bags. The rule exists precisely because fires in the cargo hold might be harder to detect and extinguish.

The FAA recommends passengers keep cell phones and other devices nearby on planes so they can access them quickly. The agency said flight crews are trained to recognize and respond to lithium battery fires. Passengers should notify the flight crew immediately if their lithium battery or device is overheating, expanding, smoking or burning.

How common is this problem?

The latest research from UL Standards & Engagement said that data from 2024 suggests that portable chargers were to blame in 19% of the incidents, though that was only slightly ahead of the number of cell phone incidents. E-cigarettes accounted for 28% of the problems.

Nearly one-third of all passengers carried portable chargers on flights last year.

More than one-quarter of passengers surveyed last year said they put vaping cigarettes and portable chargers in checked bags. That is against federal rules, but Wroth said it might be as much an issue of them not understanding the dangers as much as it is passengers trying to hide the devices.

UL Standards & Engagement, part of a safety-science company once known as Underwriters Laboratories, said it based its findings on data from 37 passenger and cargo airlines, including nine of the 10 leading U.S. passenger carriers. It is just getting ready to release this year’s report.