Emirates President Tim Clark said Monday (May 24) that the airline will refuse delivery of Boeing's 777X jets if they fall short of performance commitments.

Clark said in an interview at Dubai's Arabian Travel Market trade show that he had not received any performance details on the jet's engines so far, even though test flights began last year.

''So unless it is doing what they said it would do when we contracted, we will not take that aeroplane. So we have to see now where we're going with this. Now, we should have had the first one in June of last year, it looks as though they said the back end of 2023, but we always read that as 2024. I've been in the business too long, when I hear manufacturers say things like that, they can't give you a figure, they can't give you a date or a tail number, then you know you're shifting to the right, very often, up to 18 months."

Boeing declined to comment, and engine maker GE could not immediately be reached for comment.

Emirates is one of the U.S. planemaker's biggest customers.

It has ordered 126 777X and 30 787s worth over $50 billion at list prices.

The latest version of the 777 is still under development, and already three years behind schedule.

Clark repeated recent criticisms that Boeing needed to undertake a cultural and governance change following the production of the flawed 737 MAX.

That jet was grounded worldwide for nearly two years following two fatal crashes.