Boeing declined to comment. SunExpress, a subsidiary of Turkish Airlines and Lufthansa did not respond to a request for comment.

Boeing was due to make an aircraft order announcement later on Monday at the Dubai Airshow but the details could not immediately be confirmed.

Reuters reported on Sunday that SunExpress, which uses an earlier version of the 737, was a potential target for Boeing at the Dubai Airshow as it tries to shore up confidence in the MAX after it was grounded in March over safety concerns.

(Reporting by Tim Hepher; and Louise Heavens)