United Continental Holdings said on Thursday it was taking Boeing Co's grounded 787 Dreamliner out of its flying plans through June 5, except for a Denver-to-Tokyo route scheduled tentatively for a May launch.

United's decision came as a Japanese investigation of a fuel leak on a Dreamliner operated by Japan Airlines Co Ltd (JAL)  indicated the cause to be a coating around the mechanism that controls fuel movement between tanks. Japanese officials launched the investigation after two fuel leaks on the JAL 787, days before authorities globally grounded the new lightweight passenger jets over battery failures that sparked fires on two planes in January.

Japanese authorities still have not found the cause of the battery issue. Airlines operating 787s are setting schedules for coming months while still uncertain about when the plane will be able to resume service following the fleet's grounding five weeks ago.