WASHINGTON -- At the same time the government certified Boeing's 787 Dreamliners as safe, federal rules barred the type of batteries used to power the airliner's electrical systems from being carried as cargo on passenger planes because of the fire risk. Now the situation is reversed.

Dreamliners worldwide were grounded nearly three weeks ago after lithium ion batteries that are part of the aircraft led to a fire in one plane and smoke in another. But new rules exempt aircraft batteries from the ban on large lithium ion batteries as cargo on passenger planes. In effect, that means the Dreamliner's batteries are now allowed to fly -- but only if they're not attached to a Dreamliner.

The regulations were published on Jan. 7, the same day as a battery fire in a Japan Airlines 787 parked at Boston's Logan International Airport.

Pilots and safety advocates say the situation doesn't make sense. If the 787's battery system is too risky to allow the planes to fly, then it's too risky to ship the same batteries as cargo on airliners, they said.

"Any transport of lithium batteries on commercial aircraft for any purpose should be suspended until [an] NTSB investigation is complete and we know more about this entire issue," said Jim Hall, a former National Transportation Safety Board chairman.

Chesley "Sully" Sullenberger, a former US Airways pilot famed for his emergency landing on the Hudson River, said in an interview that he wouldn't be comfortable flying an airliner that carried lithium ion aircraft batteries in its cargo hold.

"The potential for self-ignition, for uncontained fires, is huge," he said. The new regulations "need to be looked at very hard in the cold light of day, particularly with what has happened with the 787 batteries."

The battery rules were changed in order to conform U.S. shipping requirements with international standards, as required by Congress, the federal Pipeline and Hazardous Materials Safety Administration said.

The International Civil Aviation Organization adopted the aircraft battery cargo exemption in October 2011, and it went into effect Jan. 1. Its standards normally aren't binding. But a provision inserted into U.S. law at the behest of the battery industry and their shippers says the rules can't be stricter than the UN agency's standards.

Previously, U.S. regulations prohibited the shipment of lithium ion batteries on passenger planes in packages weighing more than 11 pounds, although heavier batteries could be shipped on cargo planes.

The new rules allow the shipment of lithium ion batteries weighing as much as 77 pounds, but only if they are aircraft batteries. Shipments of other lithium ion batteries greater than 11 pounds are still prohibited. The 787's two batteries weigh 63 pounds each.

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