Boeing Co. said Friday that the aircraft fuselage proposed by Northrop Grumman Corp. in the competition between the aerospace rivals for a coveted aerial refueling tanker contract should have received lower scores from the contest’s evaluators.

The latest gripe from Boeing continues a public bickering battle between Los Angeles-based Northrop and Chicago-based Boeing over whose airframe was better suited for a $40 billion aerial tanker contract with the U.S. Air Force. Northrop was awarded the lucrative contract at the end of February and Boeing has made several appeals and attempts to discredit the award, saying initially that the entire selection process was “fatally flawed.”

Boeing has filed an official protest with Government Accountability Office, saying certain criteria slanted the award toward Northrop and added that in the long run, its version of the tanker would be cheaper to maintain. The GAO should reach a final ruling on the award of the contract by June 23.

“We think there were flaws not only in how we were evaluated, but how Northrop was,” Mark McGraw, Boeing’s tanker program manager, said in an interview Friday on Bloomberg Television. “If it was done correctly we think we might actually have won five out of five” on the major factors that the Air Force used to judge the competing bids.

McGraw also said that the fuel delivery boom on the Northrop/ European Aeronautic, Defense and Space Co. tanker had “weaknesses.”

Northrop said earlier this week that it is stopping all work on the tanker program until the GAO puts the dispute to rest.

“No amount of insistence on the part of Boeing officials that its scores should be higher will make it so,” Randy Belote, a spokesman for Northrop, said in a statement. “To raise your score, you must provide a superior product, which is precisely what Northrop Grumman did.”

Shares in Northrop were down 22 cents to $78.90 in early trading Friday.