On Monday, United Airlines announced it will stop accepting bulk shipments of rechargeable batteries amid safety concerns.
The batteries are often shipped by the tens of thousands in one cargo container on a plane, and tests by the Federal Aviation Administration over the past year have shown that just one battery overheating can transfer to others, causing a chain reaction of batteries releasing explosive gases. Several tests have ended with fiery explosions, The Associated Press reports.
Delta Air Lines stopped accepting bulk shipments on Feb. 1, but both Delta and United will still allow bulk shipments on board if the batteries are inside of something else, like a laptop, as the belief is that gives the battery a buffer. In a statement, United said, "Our primary concerns when transporting dangerous goods are the safety of our customers, our customers' shipments, and the environment."