The Pentagon's director of testing Michael Gilmore has said that the programme for the development of the next-generation F-35 fighter jet was ''on a path toward failing to deliver'' the plane's full capabilities in time, Blooomberg reported.
Blooomberg said it had in its possession the internal memo dated 9 August.
The current deadline for Lockheed is 2018. The total cost of the F-35 programme had increased to $1 trillion dollars.
Gilmore's observation also seemed to run counter to Air Force announcement that its version of the plane was combat-ready.
Gilmore wrote that in its current state, the F-35 would need support from older craft to ''locate and avoid modern threats, acquire targets, and engage formations of enemy fighter aircraft due to outstanding performance deficiencies and limited weapons carriage available.''
The current issues the plane faced, included software problems which continued to surface at a steady rate, and which Gilmore wrote interfered with target identification, communications between aircraft, and radar signal detection.
The latter would be especially significant, since the F-35 was prominently billed for its stealth capabilities.
The current version of the plane's software known as ''Block 3i,'' also left the plane's front-mounted machine gun unusable. Gilmore further wrote that flight testing had fallen ''far behind'' schedule. Operational testing of the plane was scheduled to begin in 2018.
The F-35, sometimes called the "most expensive weapon ever built," is supposed to offer different versions for the US Navy, Marines and Air Force. It was meant to replace older jets and had been approved by the Air Force and the Marines for combat, but only in limited use.
There were still two more years to go for the F-35 to go into its final test phase and then an additional year until it could go into mass production.
The Department of Defence had admitted to challenges with the development of the jet in the past. In February, the department cited over 400 problems with the jets, but said that number actually was not high for a project of the kind. A number of officials had said some of the jets could potentially be deployed within a year.