Boeing hopes to begin formally offering a longer-range version of the 737-900 to airlines by the third quarter of this year after determining whether additional wing or engine changes are required to boost the aircraft's take-off performance.

As currently configured the 737-900X would be capable of carrying a full payload over longer ranges than the smaller -800. The charter market version would incorporate an extra passenger door in the aft-fuselage to boost capacity above the current exit limit of 189 (Flight International, 6-12 February 2001).

The US manufacturer says it is determining whether prospective customers for the aircraft will require modifications to the wing or slightly more powerful engines to improve airfield performance.

"It does need a little more performance capability but it is not unsolvable," says Boeing commercial airplanes vice president marketing Randy Baseler. "The simplest thing would be to move the engine power up," he adds.

However all members of the Next Generation 737 are powered by the same version of the CFM International CFM56-7 engine and Boeing and the engine manufacturer are reluctant to introduce any hardware changes. The highest thrust rating currently available is 27,300lb (122kN).

"[Boeing] is looking at what the requirements would be and we are working together to study that," says General Electric executive vice president Bill Clapper. "The airlines like having the same bill of materials, but the balance is what is the best thing to do with the total airplane," he adds.

CFM is a joint venture between GE and Snecma of France.

The 737-900 is 2.6m (8.5ft) longer than the -800 and currently has the same maximum take-off weight (MTOW) as the smaller aircraft. Boeing aims to limit any increase in the -900X's MTOW to 4.5t.

Source: Flight International