United Airlines won't accept rechargeable battery shipments

Citing safety concerns, United Airlines on Monday became the second major U.S. airline to announce it will no longer accept bulk shipments of rechargeable batteries of the kind that power everything from smartphones to laptops to power tools.

Delta Air Lines quiet stopped accepting bulk shipments of the rechargeable batteries, also called lithium-ion batteries, on Feb. 1. It's not uncommon for tens of thousands of the batteries to be shipped in a single cargo container aboard a passenger plane on an international flight.

Federal Aviation Administration tests over the past year show that when one 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 that build up inside the cargo container. Several tests have resulted in fierce explosions that have blown the doors off containers, followed by violent fires.

The tests have placed passenger airlines in a quandary. The bulk shipments of batteries are permitted under both U.S. regulations and international aviation safety standards. They are also profitable. So far, there have been no cargo fires aboard passenger airlines attributed to lithium batteries.

But the batteries are believed by aviation officials in the U.S. and other nations to have either caused or contributed to fires that destroyed two Boeing 747 freighters in recent years, killing their pilots. The pilots of a third freighter managed to escape after landing in Philadelphia, but that plane was also destroyed.

The announcement by United to its cargo customers said the airline will stop accepting the shipments immediately.

"Our primary concerns when transporting dangerous goods are the safety of our customers, our customers' shipments and the environment," the airline said.

A third major U.S. carrier, American Airlines, stopped accepting some types of lithium-ion battery shipments on Feb. 23. But the airline is continuing to accept small packages of batteries grouped together or "overpacked" into a single cargo container. Those kinds of shipments are actually the larger safety concern because they result in very large quantities of batteries in one container.

All three airlines said they will continue to accept bulk shipments in which the batteries are packed inside or with equipment, such as laptops containing batteries or power tools with batteries inside the same package. Placing batteries inside equipment or in packaging that creates additional buffering is believed to provide added protection, although safety officials say that theory hasn't been fully tested.

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