Why some airlines won't carry lithium-ion batteries on flights

Some of the world's largest airlines are banning bulk shipments of rechargeable batteries in the face of mounting evidence of their potential to cause catastrophic in-flight fires.

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, also called lithium-ion batteries, which are used to power everything from smartphones to laptops to power tools.

Delta Air Lines quietly stopped accepting bulk shipments of the rechargeable batteries on Feb. 1. The airline said in a statement that it took the action in response to government testing and concerns raised by its pilots and flight attendants.

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 a greater safety concern because they often result in tens of thousands of batteries in one container.

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

Federal Aviation Administration tests over the past year show that when a battery overheats it can cause other nearby batteries to short-circuit and overheat, resulting in a chain reaction. As the overheating spreads, 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 most recent tests were conducted last month at the FAA's technical center in Atlantic City, N.J. They confirmed previous test results and show that overheated batteries consistently emit gases that cause explosions. The combination of gases released by the batteries varies according to the batteries' chemistry, but the gas released in the greatest volume is hydrogen, said officials familiar with the tests. Fire temperatures have reached over 1,100 degrees. The officials spoke on condition that they aren't named because they weren't authorized to speak publicly.

"Everything we find out makes it look worse and worse," said one official. "We've been very lucky so far, but at some point that is going to end and it's going to be very difficult (to explain) because everyone knows" how dangerous the shipments are.

An airliner might be able to withstand a fire generated by a small number of lithium-ion batteries, but a fire involving lots of them could destroy the plane, according to a slide presentation by Airbus engineer Paul Rohrbach. The presentation was an industry position reflecting the views of other aircraft manufacturers as well as Airbus, according to the company.

U.S. and international officials have been slow to adopt safety restrictions that might affect the powerful industries that depend on the batteries. About 4.8 billion lithium-ion cells were manufactured in 2013, and production is forecast to reach 8 billion a year by 2025. A battery contains two or more cells.

Lithium batteries dominate the global battery industry because they're cheap to make, lightweight and can hold a lot more energy than other types of batteries.

The tests have placed airlines in a quandary. The shipments are permitted under international safety standards. They are also profitable. And so far, there have been no cargo fires aboard passenger airlines attributed to lithium batteries. But as some airlines ban the shipments, it puts pressure on other airlines to follow suit or appear indifferent to safety risks.

Cargo airlines are continuing to transport the batteries even though they are believed 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.

UPS recently completed a round of tests on a shipping container that was adjusted to allow gases to escape while continuing to contain a battery fire. The company was encouraged by the results of the tests, said UPS spokesman Mike Mangeot.

U.S. regulators' hands are tied by a 2012 law that Congress enacted in response to industry lobbying. It prohibits the government from issuing regulations regarding battery shipments that are any more stringent than standards approved by the International Civil Aviation Organization, a U.N. agency, unless an international investigative agency can show the batteries ignited a fire that destroyed an aircraft. That's difficult, since in the three cases thus far in which batteries are suspected of causing fires, the planes were too damaged to determine the source of the blaze.

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