Controversy has quickly followed the US Air Force's latest attempt to revive a competition to buy 141 combat search and rescue helicopters.

Boeing has complained that the USAF has cancelled "equal information disclosure" briefings to all competitors, even as the service on 23 October released a draft copy of a third version of the request for proposals issued during the competition.

"These briefings were cancelled and are still on hold as of today," Boeing said on 24 October. "Boeing has complied and co-operated with every air force revision and request in good faith, and we believe it's time our competitors did the same thing."

The CSAR-X contract has been in dispute since 11 November 2006, when the USAF awarded the deal to Boeing to build its HH-47 Chinook.

Lockheed Martin and Sikorsky successfully protested against the award to the Government Accountability Office, and both companies later successfully challenged the USAF's terms for a recompetition, which prompted the release of the third draft of the RFP.

Boeing has complained that it faces a competitive disadvantage in the third round, as Lockheed and Sikorsky were debriefed by the USAF about the shortcomings of their original bids following its selection.

The cancelled disclosure briefings may have addressed Boeing's concerns, but instead may trigger a new round of protests. The USAF was not able to immediately comment about Boeing's concerns.

Lockheed has teamed with AgustaWestland to offer the US101. "Lockheed Martin is still in the process of reviewing the specifics of how the air force will evaluate the bids," it says. Sikorsky, which is offering the HH-92, confirms: "We received the new amendment and are still sorting through it."