U.S. transportation officials warned travelers Thursday to take precautions when flying with battery-powered gear such as laptops and cell phones after two in-flight fires involving batteries were reported in the last six weeks.

Issued by the Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA), the advisory recommends that travelers cover loose batteries with insulating tape to prevent contact with metal objects; place each battery in its own case or plastic bag; and pack spare batteries in carry-on bags rather than checked baggage.

"We're determined to keep America's airlines the safest in the world," Stacey Gerard, the PHMSA chief safety officer, said in a statement. "Passengers can help us do that by following simple precautions in packing and handling their batteries and battery-powered equipment."

On one of its Web sites, the federal agency also asked passengers to pack battery-powered devices in carry-on bags -- not those checked to the cargo hold, because fires are easier to fight in the cabin.

A pair of recent on-board fires prompted the alert. On Feb. 10, a fire broke out in the overhead bin on a JetBlue Airways Corp. flight after it had departed New York's JFK. One or more batteries were later blamed. The aircraft was able to divert to a nearby airport without incident and the fire was put out by flight attendants.

Last Sunday, a battery overheated or ignited on board an American Airlines aircraft flying from Argentina. Attendants also extinguished that fire, said the PHMSA.

The Air Line Pilots Association (ALPA), a union representing 60,000 U.S. and Canadian commercial pilots, followed the PHMSA warning with a statement of its own Thursday. "ALPA is not seeking to prohibit passengers from carrying portable electronic devices or batteries aboard aircraft, but we do want passengers to know the risk and pilots to know how to react to it," said Mark Rogers, the union's dangerous goods program director.

"A battery fire can be extremely difficult to extinguish and it may re-ignite a number of times before being controlled," Rogers added. "We're concerned that battery fires may not be routinely covered in firefighting training for crew members, and they need to know that traditional firefighting equipment may not be effective."

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