The federal government grounded Boeing’s newest and most technologically advanced jetliner Wednesday, declaring that U.S. airlines cannot fly the 787 again until the risk of battery fires is addressed.

The Federal Aviation Administration’s emergency order affects only United Airlines, the lone U.S. carrier to operate 787s. United said it would put passengers on other aircraft and work closely with the FAA and Boeing to review its fleet of six Dreamliners.

The FAA action came on the same day that Japan’s two biggest airlines — which fly almost half of the world’s 50 787s — voluntarily grounded them pending full safety checks.

Boeing said it was working around the clock with investigators.

“We are confident the 787 is safe, and we stand behind its overall integrity,” Jim McNerney, company chairman, president and CEO said late Wednesday in a statement.

The FAA decision was another setback for a plane that was supposed to establish a new standard for jet travel but has instead been beset by one mishap after another.

The latest trouble arose when pilots for Japan’s All Nippon Airways smelled something burning and received a cockpit warning of battery problems on a flight from Yamaguchi Ube airport in western Japan to Tokyo. They made an emergency landing Wednesday at Takamatsu airport in western Japan, and passengers evacuated using inflatable slides.

An inspection found that a flammable liquid had leaked from the main lithium-ion battery below and slightly behind the cockpit. Investigators found burn marks around the damage.

Japan’s Kyodo News agency quoted a transport ministry investigator as saying that the liquid leaked through the electrical room floor to the outside of the aircraft. The transport ministry said the leak could have led to an accident.

That problem followed a Jan. 7 battery fire aboard a Japan Airlines plane parked at Boston’s Logan Airport. Both incidents involved the same type of battery, raising worries that the jet’s electrical problems could be more dangerous than previously thought.

“Anytime you have a fire on board … that’s a very a serious situation on an aircraft,” said Kevin Hiatt, president of the Flight Safety Foundation.