At the 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 planes led to a fire in one plane and smoke in a second. But new rules exempt aircraft batteries from the ban on large lithium ion batteries as cargo on flights by passenger planes.

In effect, that means the Dreamliner’s batteries are now allowed to fly 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 that took firefighters nearly 40 minutes to put out.

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.

“These incidents have raised the whole issue of lithium batteries and their use in aviation,” said Jim Hall, a former National Transportation Safety Board chairman. “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.”

Chesley “Sully” Sullenberger, a former US Airways pilot famed for his precision flying that enabled passengers and crew to survive an emergency landing on the Hudson River in New York, said in an interview that he wouldn’t be comfortable flying an airliner that carried lithium ion aircraft batteries in its cargo hold.

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 in a statement.

The NTSB is investigating the cause of the 787 battery fire in Boston. Japanese authorities are investigating a battery failure that led to an emergency landing by an All Nippon Airways 787 on Jan. 16. All Dreamliners, which are operated by eight airlines in seven countries, have since been grounded.