"Virgin Atlantic has selected the Airbus A350-1000 for an order of 12 beginning 2019 to 2021 to be our large widebodied aicraft," Craig Kreeger, chief executive of Virgin Atlantic, told reporters at the show held near London.
The airline added it would purchase eight of the jets for deliveries starting in 2019, and four new aircraft on long-term leases from (leasing firm) ALC from 2020.
Airlines typically negotiate big discounts on large aircraft orders so the actual value of the deal is likely to be smaller.
The airline currently has ten A330s and 11 A340s in their fleet.
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The bumper Airbus order was hailed by British Prime Minister David Cameron, who attended the air show on Monday.
"I welcome the news of Virgin Atlantic's investment. As well as being good news for passengers, it's great news for jobs in the UK," he said.
"The fantastic Airbus A350 is part built in the UK with Rolls Royce engines and other suppliers across the country. It's an investment in the UK itself, and our world-beating aerospace industry.