About $800 million has been slashed without explanation from next year's spending plan for the Lockheed Martin F-35 Joint Strike Fighter.
The $11.2 billion budget announced on 6 April to develop and buy 30 single-engine stealth fighters was trimmed to $10.4 billion in the official Department of Defense budget unveiled a month later.
A DOD spokesperson told FlightGlobal.com the apparent reduction was not a budget "hit". The original spending estimate had not been fully developed, the spokesperson said.
The DOD has not replied to an email requesting details about the changes in the F-35 budget estimate since a month ago.
It was not clear if any element within the programme had changed as a result of the $800 million budget change.
The spokesperson's comment seemed to conflict with a statement by DOD comptroller Robert Hale, who flatly told reporters on 7 May that no major changes were made to the budget since 6 April.
Hale made the statement after a reporter asked about another discrepancy between the Gates announcement last month and the detailed budget documents. The budget reduction for the Missile Defense Agency has declined from $1.4 billion to $1.2 billion, but Hale said the $1.4 billion was stated by Gates in error.
"There are no significant changes in this budget between April 6 and what we're telling you today," Hale said.
The $10.4 billion figure apparently still reflects a plan to accelerate the F-35 purchases by 28 aircraft over the five-year period beyond FY10. From FY10 to FY15, the DOD plans to buy 513 F-35s, with 2,443 still the official programme of record.