Qantas and Jetstar will cut domestic flights for an extra three months as a result of the conflict in the Middle East and the pressure it has put on oil supplies.

The Australian airlines made the announcement on Friday.

'The Qantas Group continues to take action to mitigate the impact of the conflict in the Middle East, including sustained high fuel costs,' a statement said.

'The group has extended previously announced capacity reductions of 5 percentage points until the end of September, predominantly on Qantas and Jetstar flights on major capital city routes.'

The airline had previously said it would be introducing cuts from May until June.

Customers who were booked on flights impacted by schedule changes are being contacted directly and offered alternative flights or a refund.

Schedule changes across the group's international network have also been extended.

The Qantas Group said this was in response to strong demand for travel to Europe, with more aircraft redeployed for routes between Australia and the continent.

The airline's additional Perth-Rome flights have been extended by another three months, until the end of October. 

Services to Paris will revert to three return flights per week as planned in August and continue to operate from Sydney through Singapore.

The airline group said it has also reduced capacity on other markets, including Qantas’ Sydney to Bengaluru service, which will be temporarily suspended from August and resume at the end of October. 

Both Jetstar and Qantas have reduced capacity across the Tasman.

The announcement comes during the same week that Australian businesses have been in talks with Chinese state-owned oil companies over jet fuel sales.

Foreign Minister Penny Wong confirmed the development in Beijing on Wednesday night after meeting her Chinese counterpart Wang Yi, describing it as an early but significant result of sustained high-level engagement between the two governments.

'Following the Prime Minister's discussions with Premier Li, I can confirm that the Chinese Government is facilitating engagement with Australian businesses on jet fuel,' Wong said.

'I expressed my appreciation of this cooperation to Minister Wang Yi this evening.'

Airlines have warned existing fuel assurances may run out by the end of May as export bans and restrictions ripple across global markets.

China is Australia's largest supplier of jet fuel, making up about 30 per cent of the country's supply, and ordered refineries to halt oil exports in March.

It came amid the Middle East conflict, which resulted in the closure of the Strait of Hormuz - a crucial route for around 20 per cent of global oil flows, and approximately 80 per cent of oil destined for Australia and the broader region.

In April, Qantas Group said that around 90 per cent of its crude oil supply is hedged but jet refining margins have surged.

As a result, Qantas estimated it could be paying between $3.1billion and $3.3billion for the six months up to June 30, the second half of this financial year.

This is expected to cost the airline an additional $600million to $800million on its fuel bill for the second half of the year.

'The group is working closely with the government and jet fuel suppliers, who continue to provide confidence in fuel supply for the remainder of April and well into May,' the airline said.

'We are closely monitoring the situation, given the ongoing uncertainty in global fuel supply chains.'