United Airlines said today it is extending cancellations of Boeing 737 MAX flights from early March until June 4. That’s the longest that any U.S. carrier is scheduling without the grounded aircraft.

U.S. Federal Aviation Administration has said that Boeing still has nearly a dozen steps to complete before jets are approved for flight. That could take at least until late February or March.

Boeing said last week that it was freezing 737 production in January.

The issues came into light after two crashes, one in Indonesia and another in Ethiopia that killed a total 346 people.