(Adds quote from Sikorsky president)
WASHINGTON, May 7 (Reuters) - Sikorsky Aircraft, a unit of United Technologies Corp, won an initial $1.24 billion contract to develop and build six new U.S. presidential helicopters, the first step toward a fleet of 21 new aircraft by 2023, the Pentagon announced on Wednesday.
The award capped years of efforts by the U.S. Navy to replace the current fleet of aging Marine One helicopters, also built by Sikorsky, that ferry the president and other top officials. The Navy oversees Marine Corps procurements.
Former Defense Secretary Robert Gates canceled an earlier program managed by Lockheed Martin Corp in 2009 after the cost of the program more than doubled to around $15 billion.
The total value of the new program is expected to be around $3 billion, said Marty Hauser, director of government communications for United Technologies.
Lockheed will be the key subcontractor to Sikorsky on the new program, which is based on the Sikorsky S-92 helicopter that is already used by 10 nations for their head of state missions.
"For 57 years, our company has been trusted with the critical responsibility of building and supporting a safe and reliable helicopter fleet for the president of the United States," Sikorsky President Mick Maurer said in a statement. "We stand ready to deliver the next Marine One, the world's most advanced executive transport helicopter."
Efforts to buy a new presidential helicopter began shortly after the Sept. 11, 2001, hijacking attacks, which revealed the outdated nature of communications systems on the existing fleet.
Since 2004, Sikorsky has delivered more than 200 S-92 helicopters, mainly to companies in the oil and gas industry, and for use by civilian agencies for search and rescue.
Sikorsky was the sole bidder for the presidential helicopter after other companies opted not to compete for the work. The contract is on fixed-price terms, with an incentive fee based on the company's performance.
(Reporting by Andrea Shalal; Editing by Sandra Maler)