Delta Air Lines Inc., the world’s largest carrier, reached an agreement with pilots to rejoin a voluntary federal safety program that was created to cut the industry’s fatal-accident rate.

Delta had let the program lapse in December 2006 after a dispute with pilots over how it was administered. The resumption of the Aviation Safety Action Program leaves AMR Corp.’s American Airlines, US Airways Group Inc. and Delta’s Comair as the only major passenger carriers with pilots not taking part.

“We hope the other carriers will follow Delta’s lead and realize just how critical voluntary programs are to commercial aviation safety,” U.S. Transportation Secretary Ray LaHood said in a statement today in Washington.

Airline regulators have been pushing to restore participation in the effort, which lets pilots report safety flaws without fear of punishment. ASAP has been broadly used in the industry since 1997, and regulators and safety analysts say it has contributed to an accident-rate reduction.

The four carriers couldn’t reach consent with unions to continue ASAP after pilots said the companies were conducting separate investigations of incidents designated for ASAP. The program lapsed Dec. 15 at US Airways, and in October at American and at Comair.

The initiative will be fully restarted at Delta as early as March, Mike Pinho, a spokesman for Delta’s Air Line Pilots Association, said in an interview.

“We were able to establish administrative procedures to the satisfaction of all parties,” said Pinho, when asked if Delta will no longer have separate investigations of incidents.

By John Hughes for Bloomberg