U.S. Air Force Secretary Michael Wynne told a congressional panel Wednesday that the proposal submitted by Northrop Grumman Corp and the European Aeronautic, Defence & Space Co. was “clearly” better than a rival bid from Boeing Co.

“There were nine key performance parameters and across that spectrum, all evaluated, the Northrop Grumman airplane was clearly a better performer,” Wynne said.

Los Angeles-based Northrop late last week won the $40 billion contract awarded by the Air Force to build a fleet of aerial-refueling tankers in what many industry experts saw as an upset over Boeing. Wynne added that he thinks Boeing executives will “be debriefed on Friday,” as to why they did not receive the coveted contract which could have an eventual value that exceeds $100 billion if planes are added.

Some lawmakers and labor unions have criticized the Air Force’s award to Northrop and EADS, saying it will mean the loss of high-paying U.S. aerospace jobs.

While much of Northrop’s planes will be built in Europe, the Northrop-EADS venture plans to use hundreds of U.S. suppliers and it will conduct the final assembly in the United States, supporting 25,000 American jobs, the companies have said. The first planes are expected to enter service in 2013.

Shares in Northrop were flat at $80.23 in early trading Wednesday.