WARSAW, Poland (AP) — Polish airline LOT said Thursday it is keeping its Boeing 787 Dreamliners grounded through October while the U.S. company tries to solve a potential safety threat. The late date suggests some airlines are growing skeptical about the plane’s chances of resuming flight soon.

The world’s total fleet of 50 787s has been grounded since Jan. 16 as Boeing and investigators try to figure out why one aircraft battery caught fire and another smoldered, forced an emergency landing. Each 787 has two lithium ion batteries.