Singapore Aircraft Leasing Enterprise (SALE) announced Tuesday it will purchase up to 40 Boeing 737 single-aisle aircraft, with deliveries scheduled between the fourth quarter of 2006 and the end of 2009. The deal covers 20 firm orders and 20 purchase rights, said SALE, an affiliate of Singapore Airlines. SALE has specified the 162 to 189 seat 737-800 as the baseline aircraft for its order. Under the agreement, SALE has the flexibility to convert orders and purchase rights to the smaller 737-700, or proposed higher capacity 737-900X, which can seat up to 215 passengers. "The next-generation 737 series is a popular choice with carriers from all geographic regions and every segment of the industry," said SALE Managing Director Robert Martin. SALE also has outstanding firm orders with Boeing's rival Airbus for 11 A320s, due to be delivered between now and the end of the second quarter of 2006.