BOEING Co and Northrop Grumman Corp, competing to win a reopened US$35 billion United States Air Force's refueling tanker contract, said they met Department of Defense officials on Saturday for the second time in a week to move forward on an amended bid proposal.

"Through its protest, Boeing got what it asked for, which was clarification of exactly what is required to meet the air force's tanker requirements," said Northrop spokesman Randy Belote in an e-mail after company executives met officials at the Wright-Patterson Air Force Base in Dayton, Ohio.

The meetings to discuss new guidelines for the reopened contest come after the Government Accountability Office upheld a protest by Boeing, saying that the air force made "significant errors" in awarding the contract to a Northrop team in February, Bloomberg News said.

The companies met government officials last Tuesday and afterward Boeing said it wanted "more discussions" while Northrop said the company was "pleased" with the process to date.