Tokyo, Jun 5 (IANS/EFE): Japan's two main airlines, JAL and ANA, have been ordered to thoroughly inspect all of their Boeing 787 Dreamliners after last weekend's discovery of a problem with one of JAL's planes, Transport Minister Akihiro Ota said.

He also directed the two companies to review their methods for supervising maintenance work performed by manufacturer Boeing, who had modified the battery of that JAL aircraft after the series of technical problems that forced authorities to ground all 787s for about four months.

The incident involving the JAL Boeing 787 Sunday came just a day after both firms had resumed commercial flights with Dreamliners for the first time since Jan 16.

On Sunday, the pressure sensor on the plane's battery cover registered a difference in air pressure between the exterior and the interior of the battery container during a pre-flight safety check.

According to JAP, the pressure differential occurred due to faulty maintenance by Boeing.

Problems with the 787 fleet have been mounting since January, when a series of failures in the planes' lithium-ion batteries forced authorities to suspend operations with the almost 50 jets used by airlines around the world.

After approving the improvements in the new batteries redesigned by Boeing, US and Japanese authorities in April gave the green light to resuming 787 flights.