The estimated total price for research and procurement has increased by $22 billion in current dollars adjusted for inflation, according to the Pentagon’s latest annual cost assessment of major projects.

Defence Department’s latest Selected Acquisition Report sent to Congress last week underlines an increase to $428.4 billion from $406.2 billion in acquisition costs, about a 5.5 percent increase.

The Report states that the increase isn’t due to poor performance, delays or excessive costs for labour or materials. Instead, the increase reflects for the first time the current cost estimates for a major set of upgrades planned in coming “Block 4” modifications.

“Ensuring our Block 4 efforts are captured in our acquisition baseline and now in our SAR help us to provide full transparency and status on our F-35 modernization progress,” the Pentagon’s F-35 program office said in an emailed statement.

The additional $22 billion cost for the Block 4 upgrade only includes U.S. aircraft; aircraft operated by foreign countries will be costed – and paid – separately.