All Nippon Airways (ANA) said it continues to assume the Boeing 787 will be grounded through the end of May, but it has yet not decided how it will handle 787-designated routes from June 1.

ANA, which had 17 787s in its fleet when the worldwide Dreamliner fleet was grounded Jan. 16, issued a schedule update Friday in which it reiterated the suspension of a number of routes through May 31 owing to the 787’s unavailability. These include Tokyo Narita-Seattle, Narita-San Jose, Kansai-Seoul and Nagoya-Seoul.

The airline said it has “yet to be determined” whether it can commence those routes from June 1 and is holding off on extending the suspension of the routes on its schedule beyond May 31. Boeing chairman, president and CEO Jim McNerney said Thursday the company has “a high degree of confidence” in the revamped 787 battery system it is in the process of testing and believes the 787 will be cleared to fly again commercially “sooner rather than later.”

ANA is also planning to launch a second daily flight on the Narita-Chicago O’Hare route from June 29, but has indicated it will need the 787 to be available to do so.   

“ANA will continue to cooperate with all parties and make all efforts to ensure and confirm the safety of this aircraft, so that 787 flights may recommence as soon as possible,” the airline said in a statement.