Lancashire-based BAE Systems has sealed a £2.5bn deal with Oman. BAE will provide the Gulf state with 12 Typhoon fighter jets and eight Hawk training jets.
David Cameron has defended the deal with Oman, saying it will safeguard thousands of jobs including at the BAE Systems factory in Lancashire.
The deal is to be sealed when the Prime Minister visits the country.
The Middle Eastern state and BAE Systems are also expected to finalise the sale of eight Hawk 128 aircraft.
Before his arrival in Muscat, the Prime Minister dismissed concerns about Britain selling arms in the region.
"Boosting exports is vital for economic growth and that's why I'm doing all I can to promote British business in the fastest growing markets so they can thrive in the global race," he said.
"Every country in the world has a right to self-defence and I'm determined to put Britain's first-class defence industry at the forefront of this market, supporting 300,000 jobs across the country.
"It's testament to Britain's leading aerospace industry and the deal will safeguard thousands of jobs across the UK, not just at the BAE Systems factories in Lancashire and East Riding in Yorkshire but at many more small businesses up and down the country that play a vital role in delivering these aircraft."