With the 757 series going out of production, the 739 is now Boeing's largest narrow body airliner. While the 739 is not as versatile and has less range than a 757, it is lighter will lower operating costs.....however, the 739 can certainly operate most routes that are generally flown by the 757. I would expect there will be increased interest in the 739 in the coming years as passenger numbers increase. The 739 would be a very practical choice for any airline that now operates any member of the 737NG to add a higher-capacity airliner.
With all of the "excitement" at Boeing focused on the 7e7, a possible 747 update and the new 777 models (-200LR and -300ER), little has been said about the proposed 737-900X (or -900ER)....which would give the 739 more range and allow it to operate US transcon flights with little or no weight restrictions. The 739 was a simple strech of the 738, meaning that the 739 traded some range for its increased size and capacity. It was long speculated that Alaska would be the launch customer for this new type, but nothing thus far has materialized and AS
recently swapped a couple of 739 orders for 738s (it is likely that the AS
738s will be dedicated to their SEA
-Florida routes).......it was also rumored that the 739X would deal with the emergency exit issue which would allow increased seating on the type when configured in a high density seating arrangment. The 739X, with increased range and seating, would be very attractive to European charter carriers which operate the 737NG, carriers such as Air Berlin, Hapag-Lloyd and Transavia.