Sheikh Ahmed said the deal raises total outstanding orders from USA aerospace giant Boeing, the global competitor of Europe's Airbus Industries, to as high as $90 billion.
Emirates Airline yesterday announced the next stage in assembling its future fleet when it signed a memorandum of understanding to buy 40 Boeing 787-10s.
Emirates is by far the largest buyer of the world's largest passenger jet, the A380, with 142 on order and 100 already delivered. "We have reached a conclusion that the Boeing 787-10 jets are the best choice for us", 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".
With 737 MAX deliveries due to end in 2023, "we are definitely interested in a new order; we are working on a new order", al-Ghaith said in an interview.
The company is still looking at which engine will power the 787-10s, with a decision expected "very soon".
"Emirates' endorsement of the 787 Dreamliner extends our long-standing partnership and will sustain many jobs in the United States".
Industry sources say at least one of the ex-Singapore jets will be operated by Portugal-based HiFly.
The importance of the order was underlined by the presence of the vice-president and prime minister of the UAE, and ruler of the Emirate of Dubai, Sheikh Mohammed bin Rashid Al Maktoum, at the announcement.
The airline posted a net profit of $452 million in the period from April to September, up 111 percent on the same period a year ago.