United Airlines says it won't accept rechargeable battery shipments, citing safety concerns

Citing safety concerns, United Airlines says it will no longer accept bulk shipments of rechargeable lithium batteries of the kind that power everything from smartphones to laptops to power tools.

United is the second major U.S. airline to decide it will no longer accept lithium-ion battery shipments. Delta Air Lines stopped accepting the bulk shipments last month.

It's not uncommon for tens of thousands of the batteries to be shipped in a single cargo container aboard a passenger airliner on an international flight.

Federal Aviation Administration tests over the past year show that when a single battery overheats it can result in a chain reaction, causing other batteries to short circuit and overheat. As they overheat, the batteries emit explosive gases. Several tests have resulted in fierce explosions and fires.