The US Department of Defense and Lockheed Martin have agreed in principle to the next yearly production contract for 43 F-35s worth $4.3 billion that lowers average unit costs by 3.6%.

The announcement is expected to be followed by a signed contract in the “coming weeks”, Lockheed says.

The promised, 3.6% unit cost reduction comes a year after Lockheed signed a $3.9 million contract for 35 F-35s in the seventh year of low-rate initial production (LRIP).

That number implies that the average unit cost across all three variants has declined from $111.4 million in LRIP-7 to about $107 million in LRIP-8.

Lockheed officials are not able to confirm the actual unit cost average until the contract is signed.

That total does not include the cost of the Pratt & Whitney F135 engine.

The LRIP-8 contract includes orders for 29 US fighters and 14 international fighters, including the UK’s four F-35Bs, Japan’s four F-35As and two F-35A’s each for Israel, Italy and Norway. The US Department of Defense is buying 19 F-35As, six F-35Bs and four F-35Cs.

More than 200 F-35s are now under contract for delivery through the end of Fiscal 2016.