Azerbaijan Airlines signed an agreement with Boeing placing a firm order for five 787-8s and committing to order two very large freighters, either the 747-8F or the 777F.
Emirates group chairman, Sheikh Ahmed bin Saeed Al Maktoum, said that airline's management had looked at both aircraft "and came to the conclusion that the 787 would be the better option".
Delivery of the Dreamliners is scheduled to start in 2022, he said on the first day of the Dubai Airshow.
"This is a long-term commitment that supports hundreds of thousands of jobs, not only at Boeing but also throughout the aviation supply chain", Sheikh Ahmed said.
Asked at a news conference on the launch of a new first-class cabin whether Emirates would place an A380 order at the show, Emirates president Tim Clark said, "maybe, maybe not". "We always take the future into consideration and what is happening in the UAE". "This aircraft will open new destinations around the world for us".
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The 544-seat jet entered service amid huge fanfare in 2007, but its future has been thrown into doubt by sluggish sales as airlines turn to efficient smaller jets like the Boeing 777, of which Emirates is also the largest buyer.
Securing the new order from Emirates, which is by far the largest customer for the A380, clears a major hurdle to extending production towards the middle of next decade.
Industry sources say at least one of the ex-Singapore jets will be operated by Portugal-based HiFly.
The airline posted a net profit of $452 million in the period from April to September, up 111 percent on the same period previous year.
The rise in earnings was driven by "capacity optimisation and efficiency initiatives across the company, steady business growth, and a more favourable foreign exchange situation compared to the same period past year", the airline said.