Boeing hopes to extend the life of its F-15 production line with the unveiling of a new variant to incorporate stealthy coatings and structures.

Company officials say the new F-15SE "Silent Eagle" - designed under a secret project called "Monty" - could garner up to 190 sales abroad, especially to nations already operating F-15s. The target market is South Korea, Singapore, Japan, Israel and Saudi Arabia.

With Silent Eagle, Boeing is "slipping into the silent cloak of stealth," says Dan Korte, vice president and general manager of Global Strike Systems.

South Korea is the likely first customer: Seoul expects to embark on its F-X3 program soon, with a goal of buying about 60 F-15-class aircraft. A request for proposals is expected in the first quarter of 2010, with a downselect to a winner later in the year. A contract would follow in the first quarter of 2011.

The current F-15 backlog is 38 aircraft, with deliveries to both Singapore and South Korea pending. The production rate is about 12 per year, and that can be increased depending on demand.

The fate of Boeing's workforce in St. Louis is uncertain beyond the 2014 time frame. That's because Lockheed Martin won the massive Joint Strike Fighter competition and established the "fifth-generation" fighter market, capturing a host of international customers. Boeing also lost out on government-funded stealthy UAV work since losing the Navy Unmanned Combat Air System contract to Northrop Grumman last year.

Orders remain strong for the F/A-18E/F and EA-18G made here; they are expected to carry through 2014, including deliveries to the U.S. Navy and Australia.

St. Louis is also the site of manufacturing for the T-45 and some C-17 structures; but the C-17's future is murky, and the program has survived only with congressional intervention.

The idea behind the Silent Eagle is to capture orders from existing F-15 countries by adding what Boeing officials say are inexpensive modifications to the aircraft. But they say they're not targeting the market already served by the F-35 and F-22.

Stealthiness for the F-15 was explored about a decade ago for the U.S. Air Force as an alternative to the F-22, but it was dashed once the twin-engine Lockheed Martin Raptor program took root.