Singapore Airlines Ltd says it has placed an order for 20 Boeing B777-200 aircraft worth $4.0 billion (over £2.7 billion).
The order, which includes 10 firm orders and 10 options, includes the cost of aircraft spare parts and engines.
"These aircraft will replace an existing fleet of A310-300 aircraft and cater to growth," says the airline.
The 20 planes, which will be powered by Rolls-Royce Trent 892 engines, will be delivered between 2003 and 2009. They will be be used mainly on regional routes, although the plan is also suitable for longer routes.
The airline says it expects to finance the purchase largely from its cash flow but may also consider borrowing funds or leasing the planes if necessary.