Russia and Indonesia finalized a deal for the purchase of 11 Sukhoi Su-35 multirole fighter jets, Interfax reported citing a military source.

The contract was signed to replace Indonesia’s outdated F-5 Tiger planes, which had been in use since 1980. Indonesia previously planned to purchase 10 of the jets but later accepted a Rostec proposal for 11 planes.

On February 6, Tass reported that Russia and Indonesia were on the verge of agreeing the technical details of the contract. Negotiations began in November 2015 but were apparently held up over countertrade deals and offset obligations. Indonesia requires countertrade in certain commodities to offset at least 35 percent of the value of aircraft purchases.

Russia has pledged to buy commodities to offset about 50 percent of the value of the contract, worth around $1.14 billion (S$1.4 billion) and provide transfer of technology worth an additional 35 percent, Straits Times reported last month.

Delivery of the first two aircraft to the Indonesian Air Force is expected by October, according to IHS Jane’s.

The Su-35 is a multirole 4th generation super-maneuverable thrust-vectoring fighter jet equipped with a phased array radar. The aircraft’s top speed is reportedly 2,500 kilometres and it has a combat radius of around 1,600 kilometres. It carries a 30mm gun and has 12 hardpoints.