ARLINGTON, Va., March 4 (UPI) -- Last week Northrop Grumman (NYSE:NOC) and its European partner EADS confounded expectations by beating incumbent Boeing for the contract to build the U.S. Air Force's next-generation aerial refueling tanker.

The initial contract will be for 179 modified wide-body jets, but eventually the entire fleet of 600 Cold War tankers will need to be replaced, making this one of the biggest marketing coups in defense-industry history. However, that is just the beginning of what Northrop Grumman has achieved, because Boeing didn't manage to beat Northrop Grumman in a single measure of merit. Here's how they were evaluated:

First -- Mission capability: Arguably the most important factor, this metric compared the teams on performance requirements, system integration & software, product support, program management and technology maturity. The teams tied in most measures, but the Northrop Grumman offering was deemed to offer superior refueling and airlift capacity at 1,000 nautical miles range and substantially superior refueling and airlift capability at 2,000 nautical miles range. The superior airlift capacity of Northrop Grumman's plane was deemed a "compelling" consideration in giving Northrop Grumman the edge for this factor.

Second -- Proposal risk: This is the sole factor in which Boeing managed to match the appeal of the Northrop Grumman proposal, but it did so only after being pressed to accept a longer development schedule for its tanker. The Boeing (NYSE:BA) proposal was initially rated as high-risk because reviewers felt the company was offering a plane that in many regards had never been built before, and yet claiming it could be built fast at relatively low cost. The company was forced to stretch out its aggressive schedule, adding cost.

Third -- Past performance: The Northrop Grumman (NYSE:NOC) team received higher ratings in past performance due to satisfactory execution of half a dozen programs deemed relevant to the tanker competition. U.S. Air Force reviewers had less confidence in Boeing's past performance due to poor execution in three relevant programs. In addition, Northrop Grumman's subcontractors were rated more highly on past performance than Boeing's.