By Andrea Shalal-Esa
WASHINGTON (Reuters) - U.S. Air Force and Boeing Co officials on Wednesday expressed confidence that a $52 billion air refueling program would deliver its first 18 planes by August 2017 as scheduled, despite a Pentagon report warning that testing of the new aircraft could be delayed by at least six to 12 months.
The tanker project known as KC-46, one of the Pentagon's biggest arms programs, calls for Boeing to build 179 new planes for the Air Force to replace the current fleet of 50-year-old KC-135 tankers. The planes are used to refuel fighter jets and other warplanes during flight.
Air Force and Boeing officials have said the program is making good progress, with the last of four test planes to be completed this year.
But a report released Wednesday by the Pentagon's chief weapons tester, Michael Gilmore, said Boeing and the Air Force needed more time to complete developmental testing and initial training before operational testing.
"The KC-46 development test program is aggressive but achievable," said Air Force spokesman Ed Gulick in a statement, responding to the new Pentagon report.
He said a recent risk assessment by the Air Force's KC-46 program office found that Boeing had a "greater than 90 percent probability" of meeting its contractual obligation to deliver 18 jets by August 2017.
Boeing said the program was hitting all its milestones.
"We remain confident in our plan to support Initial Operational Test & Evaluation for the KC-46A tanker and we continue to meet our contractual requirements," said spokesman Jerry Drelling. "We have a valid flight test plan in place and ... remain on plan to deliver the first 18 combat-ready tankers to the U.S. Air Force by 2017."
Gulick said the Air Force planned to begin initial operational testing of the new jets, which are based on Boeing's 767 commercial airliners, in May 2016.
He said a number of measures had been put in place to lower the risk of delays, including agreements with outside agencies and use of Boeing's vast commercial flight test resources.
The program is also using a "Test Once" concept based on Boeing's commercial practices, under which flight tests satisfy different requirements mapped out by Boeing, the Federal Aviation Administration, developmental testers and, where it makes sense, operational testers.
Boeing has delivered more than a thousand 767s worldwide.
The KC-46 tanker program has been closely scrutinized since its decade-long contest with France's Airbus and an ethics scandal resulted in two Boeing officials getting sentenced to prison in 2004.
(Reporting by Andrea Shalal-Esa; Editing by Kenneth Maxwell)