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PARIS (Reuters) - Norwegian Air expects Boeing’s 737 MAX aircraft to remain grounded until at least the end of August, missing the European summer season, CEO Bjoern Kjos said on Friday.

“If you ask Boeing they still say June or July,” Kjos said at the Paris Air Forum. “But we’re already in mid-June - we’ve planned for the MAX to be out until the end of August.”

More than 300 Boeing 737 MAX jets have been grounded worldwide after two fatal crashes in Ethiopia and Indonesia killed nearly 350 people. Some airlines now expect the plane to remain out of action until the end of 2019.

Norwegian, which operated 18 of the planes, has said the grounding will raise its costs by up to 500 million Norwegian crowns ($58 million). The low-cost, long-haul operator has delayed disposal of older Boeing 737 models or prolonged leasing contracts while it waits for their MAX replacements.

Boeing is awaiting a decisions by the U.S. Federal Aviation Administration on software improvements it proposed after the crashes and whether to require additional pilot training before flights can resume.

If more training is ordered, a shortage of simulators means that “it might be much longer” before commercial flights resume, Kjos said. “For some operators it could take up to a year.”

As a customer of Boeing’s GoldCare maintenance program, however, the CEO said Norwegian might not have to wait that long.

“We’d hope to be at the front of the queue,” he said.