Qantas passengers with unused travel credits could be given an extension to cash them in, as the airline fends off concern the money is propping up its bottom line.
Flight Centre chief executive Graham Turner said there was a high chance the Flying Kangaroo could defer the date for when the travel credits issued during the height of the COVID-19 pandemic would expire.
The credits are due to expire at the end of the year.
Qantas chief executive Alan Joyce said the value of its flight credits was $100 million higher than the $370 million reported, with $100 million in credit yet to be redeemed by Jetstar customers.
No amount has been given for overseas bookings.
But Mr Turner said it was in Qantas's best interest to extend the deadline by when the credits would need to be redeemed.
"Qantas will probably extend it again," he told Seven's Sunrise program on Wednesday.
"They've extended it three times, just because the lack of capacity means that if people want to transfer on another flight or book other flights, it can be quite hard to get a booking when you wanted.
"Some of these credits come back to three years old - and after a year a lot of the records are purged - so it is difficult (to redeem), particularly people who booked directly online."
Prime Minister Anthony Albanese said people who had booked flights with Qantas should be able to reuse the credit or get their money back.
Qantas is rolling out a major communication program to alert passengers to the credits.
The government had come under fire for blocking additional Qatar Airways flights to Australia after lobbying from Qantas.
Mr Turner said the extra flights would lead to lower international airfares for passengers.
"We desperately need more capacity and this was not a good decision from our point of view," he said.
Former head of the consumer watchdog Allan Fels said the move by the government lowered competition in the industry.
"(The government's rationale) is to look after Qantas," he told ABC TV.
"Customers have been put second - so has tourism, business freight, many other interests, also other airlines
"There's no secret reason for it.
"It's just looking after Qantas."
The government said the decision was in the national interest but declined to elaborate.
Opposition Leader Peter Dutton said the government had signed a "sweetheart deal in secret" with Qantas and called for the prime minister to be honest with Australians.
Nationals leader David Littleproud said the higher flight prices were also hurting agricultural exporters.
"This takes away our competitive advantage and capacity as well, so it goes far more reaching than just tourism," he told ABC TV.
"We have serious concerns about how the minister got to this junction and the prime minister is quickly trying to wipe his hands of it, saying that it was not his call."
Prof Fels said the Australian Competition and Consumer Commission should investigate the government's decision.
Qantas declined to comment.