Emirates airline's president said he is unsure if the world's biggest long-haul airline will receive its first Boeing 777x jetliner before 2024, casting doubts on the delivery timeline of the long-delayed jet scheduled to debut in 2023. The aircraft is due to be delivered by 2023 but Emirates will not take any planes unless they fully meet contractual specifications, Tim Clark told aviation consultant John Strickland in an interview broadcast on Monday. The aviation veteran said he still has not seen any data on the aircraft's engine performance capabilities to date, despite the plane undergoing test flights since last year and Boeing already building 11 of them. "We will not accept a plane unless its performing 100 per cent to contract, in the same way they expect us to pay 100 per cent to contract at delivery," Mr Clark said during the session of the Arabian Travel Market online conference. "Unless it’s doing what they said it will do … we will not take that aeroplane." Long-haul carrier Emirates is the biggest operator of Boeing 777s, with about 140 of the jets in its fleet, and plans to replace the retired aircraft with the new 777X version of the wide-body model. Boeing has said it will debut the revamped plane in 2023, three years later than it originally planned. "There are issues on the airplane, I'm not clear as to when we're actually going to get them," Mr Clark said, pointing to the "stigma" around Boeing's 737 Max and how that could affect certification of their new aircraft. Emirates, a launch customer of the 777X, ordered 126 of the planes from the Chicago-based manufacturer. "We should have had the first one in June of last year, they have said the back-end of 2023, we always read that for 2024," Mr Clark said. Mr Clark said it was time for Boeing to undertake a "deep-rooted soul-searching" about its business culture after production issues on the 737 Max, which was grounded globally for almost two years following two fatal crashes. "Learn from it, don't make the same mistakes constantly as you seem to be doing in the last 10 or 15 years, I say to Boeing," Mr Clark added, pointing to production issues that have also affected Boeing's 787 Dreamliner. In the broadcast interview, the industry veteran also said that Emirates and low-cost sister company Flydubai, which have deepened their ties in recent years, will work closer together but will not merge into a single entity. "The brands will remain separate but going forward will operate far more closer than they have perhaps done in the past," he said. Emirates is currently performing better, compared to a year ago when the Covid-19 pandemic first disrupted air travel. "We are a lot further on and much better than we thought we would be at this time," he said. Air travel demand will return at a "staggering rate" if the global vaccine campaign keeps progressing, he said. "The ideal situation is that the vaccine programme beats the virus in its many mutations and that we're on top of that ... let's say by autumn of this year – October, November, December – you get some kind of relief from all of that, demand will come back at a staggering rate," he said. "International travel, on the basis of that scenario, will return in large numbers, I don't doubt that at all." However, cheaper and faster PCR testing, governments better aligning travel protocols and equitable vaccine distribution will help unlock this pent-up demand. "It's a question of seeing how we navigate the next six months and if we do it right – equitable rollout of vaccines to scale, testing regimes are simplified and made cheaper – all this lends to the theory that by the end of the year, we will be back in business at some scale," he said. "But we have to wait and see."