Mr Sears was seen as a potential Boeing boss

On Monday, Mike Sears - Boeing's number-two executive - was sacked by the firm for unethical conduct.

Boeing said he helped hire Darleen Druyun, a US Air Force official, before she had officially disqualified herself from government service.

But in a statement, Mr Sears said he was "disappointed" by Boeing's actions.

"At no time did I engage in conduct which I believed to be in violation of any company policy," Mr Sears said in a statement issued through his lawyers.

"At all times, I have faithfully carried out my duties on behalf of Boeing to the best of my ability," he said.

"I am deeply disappointed by the action the company took."

Illicit communication

Boeing fired Mr Sears following indirect communication with Ms Druyun over negotiations for a massive contract to convert 767 jets to military refuelling tankers.

According to Boeing's internal investigation, Ms Druyun - previously a top procurement official in the Air Force - passed on pricing data from Airbus, Boeing's closest rival in the international aviation market.

In return, the complaint implied, she was offered employment at Boeing.

Ms Druyun was also dismissed on Monday.

Delay?

On Tuesday, US Defence Secretary Donald Rumsfeld said he had asked officials to look into whether the contract should be delayed.

"We're the custodians of the taxpayers' dollars," he said.

"We have an obligation to see that things are done properly."