It's being billed as the largest private order in aviation history and Bombardier Inc.'s business jet division is getting a big chunk of it.

NetJets, a unit of Warren Buffett's Berkshire Hathaway Inc., announced late Monday that it has signed an order with Bombardier and rival Cessna Aircraft Co. for up to 425 new business jets valued at up to $9.6-billion (U.S.).

The order represents a huge vote of confidence on the part of Mr. Buffett – the legendary Omaha, Neb.-based billionaire investor – in the future of the luxury air travel business.

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NetJets, based in Columbus, Ohio, has a fleet of more than 700 aircraft around the world. It provides fractional ownership to customers who buy a certain percentage of an aircraft and are given a fixed amount of flying time per year.

NetJets said it plans to buy up to 150 Cessna Citation Latitudes – starting with 25 firm orders, and options for 125 more.

From Bombardier, NetJets will buy up to 275 Challenger 300 and 605 series jets – 100 firm orders and options on another 175.

"This purchase demonstrates our long-term planning and represents our ongoing commitment to providing unparalleled safety and service in aircraft uniquely customized for our owners," NetJets chairman and chief executive Jordan Hansell said in a statement.

"By increasing the range and endurance of our fleet, we will allow our owners to get to even more destinations worldwide," he said.

NetJets customers include corporate clients and high-net-worth individuals.

The order for Bombardier's Challenger jets is valued at about $7.3-billion.

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Bombardier said it's the largest Challenger order in its history.

Montreal-based Bombardier said it has also won a 15-year maintenance agreement for the aircraft that could reach $2.3-billion in value.

The firm orders alone, 75 for the Challenger 300 and 25 for the roomier Challenger 605, are estimated to be worth about $2.6-billion.

Bombardier has seen business-jet orders bounce back recently after a slowdown during the global financial crisis.

Earlier this year, NetJets said it planned to order up to 120 of Bombardier's Global business jets, a transaction valued at about $6.7-billion.

"We are very proud that, once again, NetJets has selected Bombardier aircraft to grow and support the expansion of its fleet worldwide," Bombardier Business Aircraft president Steve Ridolfi said.

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Besides manufacturing business jets, Bombardier also has its own fractional jet business: Flexjet.