Washington ? Lawmakers on Thursday demanded a detailed explanation of what went wrong with the Air Force’s management of a $35 billion tanker contract awarded to Northrop Grumman Corp. and its European partner over Boeing Co.

Congress sought clarity from a Defense Department official and congressional investigators on whether the recent competition’s failure was confined to the Air Force, or indicative of a more systemic problem among the Pentagon’s procurement process.

Lawmakers also pressed for details on how the Pentagon would proceed with the re-competition of the tanker deal that Defense Secretary Robert Gates announced Wednesday to avoid future mistakes.

Gates said the Air Force would no longer oversee the tanker competition, and appointed Pentagon acquisition chief John Young and a dedicated source selection committee to take over the process.

Young on Thursday reassured lawmakers the Pentagon would try to mitigate or avoid any more mistakes, including doing a better job of explaining to both competitors the most valued requirements in a new aircraft.

The Government Accountability Office last month detailed “significant errors” the Air Force made in the original award to Northrop and Airbus parent European Aeronautic Defence and Space Co. The GAO said Chicago-based Boeing, which protested the deal, might have won had the service not made mistakes in evaluating the bids.