The lithium ion batteries that are causing problems for Boeing’s new 787 Dreamliner have been causing problems for some time. Japan’s All Nippon Airways says even before the most recent string of 787 incidences, it had to repeatedly replace many of the batteries because they weren’t working properly.

While Japan Airlines admits it also changed the batteries in a few cases. All 50 of Boeing’s 787s in use around the world remain grounded after problems with the batteries on two aircraft earlier this month.

The BBC’s Rupert Wingfield Hayes says Boeing was aware of the battery changes but that the airlines “didn’t inform the NTSB (National Transportation Safety Board) or the Japanese authorities because they say these were not issues that were a threat to the safety of the aircraft. They say it was things like the batteries wouldn’t recharge properly, they wouldn’t hold a charge, those sorts of issues which you also get with your laptop battery or your phone battery… But it looks like there is a pattern that maybe the authorities should have been told about”.

The Federal Aviation Administration says the airlines must demonstrate battery safety before flights can resume.