United grounds Boeing 787

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CHICAGO, Feb. 22 (UPI) -- Chicago's United Airlines says it is keeping its fleet of Boeing 787 airplanes grounded until June 5 over concerns about the aircraft's battery system.

United is the only U.S. airline to utilize the Boeing 787 and has six of the planes in its fleet, the Los Angeles Times reported Thursday.

"We are taking the 787 out of our schedule through June 5, except for Denver-Narita, which will tentatively launch on May 12," said Christen David, a spokeswoman for the airline.

United's grounding of the planes came after the Federal Aviation Administration grounded the Boeing 787 Dreamliner fleet after two incidents occurred within two weeks involving the plane's lithium-ion battery systems.

The first of such incidents happened on Jan. 6 aboard a parked 787 in Boston operated by Japan Airlines. A fire started inside the plane. The National Transportation Safety Board is still investigating the cause of the fire, but earlier this month said investigators found a short circuit in one of the aircraft's batteries.

Then, on Jan. 16, Japanese carrier All Nippon Airways had to make an emergency landing after receiving a warning of a battery failure. Japan's Transport Safety Board has been investigating the circumstances that led to the incident.