Qantas and Jetstar are cancelling flights scheduled for the second half of 2022 due to Australia's surge in COVID-19 cases.

The Qantas Group has advised it will be cutting back its flights planned for July, August and September as the expected number of passengers wanting to fly has dropped off.

The company had been planning for demand for flights to be at 102 per cent of the levels before the pandemic.

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However, following the recent surge in COVID-19 cases across the country, the demand for the third quarter of the year is expected to only be at 70 per cent of pre-pandemic levels.

"The sudden uptick in Covid Cases is having an obvious impact on consumer behaviour across various sectors, including travel, but we know it's temporary," Qantas Group CEO Alan Joyce said.

The expected demand for international travel in the same period has fallen from 30 per cent to around 20 per cent of pre-COVID levels due to increased travel restrictions in countries like Japan, Thailand and Indonesia.

Qantas customers will be contacted directly from late January if their booking is impacted by cancellations and offered alternative flights that will be likely to be a difference of a few hours for domestic travel.

The company has said it will continue to utilise all of its crew despite the cancellation of flights.

Mr Joyce said the company was optimistic that the demand for flights would not take long to return to normal.

"This is a difficult time right across the community, but something we'll get through," he said.

Due to COVID-19 uncertainty, Qantas has extended its Fly Flex program, which enables customers to change their travel dates.