WASHINGTON — Two major U.S airlines say they will no longer accept rechargeable battery shipments as new government tests confirm that explosions and violent fires are likely to occur when large numbers of batteries enclosed in cargo containers overheat.
Tests conducted last month by the Federal Aviation Administration show that rechargeable batteries, also called lithium-ion batteries, consistently emit explosive gases when they overheat or short-circuit, The Associated Press has learned. In the recent tests, as well as other FAA tests last year, the buildup of gases — primarily hydrogen — led to fierce explosions.
An FAA video of one of the tests obtained by the AP shows an explosion knocking a cargo container door off its hinges and tossing boxes of batteries into the air. The container was engulfed in fire minutes later.
In the test, a cartridge heater was used to simulate a single battery overheating. The heater caused nearby batteries to overheat and the short-circuiting spread to many of the nearly 5,000 batteries in the container. It's common for tens of thousands of batteries to be placed in a single container.
Citing safety concerns, United Airlines on Monday informed its cargo customers it will no longer accept bulk shipments of the 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 are the kinds of shipments that the FAA has been testing and that are a greater safety concern.
All three airlines said they will continue to accept bulk shipments of equipment containing batteries or in which batteries are 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.
The decisions by United and Delta airlines could put pressure on other international carriers to refuse battery shipments or appear indifferent to safety.
"I think it will cause everybody to take a look at their policies and procedures as far as carrying that cargo, and many will elect not to," said John Goglia, a former National Transportation Safety Board member and aviation safety expert.
Airline industry analyst Robert W. Mann said, "It's only a matter of time before a really serious event occurs."
Airlines "are essentially just trying to avoid that occurrence," he said.
Temperatures in some of the government testing reached nearly 1,100 degrees. 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.
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.
Follow Joan Lowy on Twitter at http: //www.twitter.com/AP_Joan_Lowy