Singapore Airlines plans to buy up to 31 Boeing B777-300ER (extended range) aircraft.
Eighteen of the 31 are firm orders for delivery between 2006 and 2010, while the remaining thirteen are subject to exercise of purchase rights.
At list prices, the order is worth approximately US$7.35 billion, including the cost ofspares and spare engines, the airline said.
Chief executive officer Mr Chew Choon Seng said: "With its use of new generation avionics and materials, and its higher operating efficiency, the B777-300ER will deliver lower operating costs.
"It should integrate well with our existing fleet."