Regional airline Rex has decided to abandon Adelaide's new $260 million terminal in yet another blow to the airport's operators, by moving its inbound flights and operations to the unused former international terminal by the end of the month.

In a bid to soothe passenger concerns about long walks to collect baggage and unnecessary inbound security checks, the airline will negotiate its move this week, including the need to use a bus to take passengers directly to the old terminal.

"There are still some issues we need to discuss with the major airlines," said Rex managing director Geoff Breust yesterday.

"(And) Adelaide Airport Limited needs to do some work with the old terminal to ensure it can be used again."

The old international terminal has been idle since its flights began using Adelaide's new $260 million airport in October last year.

But while international airlines began using the terminal immediately, domestic airlines faced a three-month delay caused by contaminated fuel pumps and the cleaning of fuel pipes.

The protracted delay embarrassed airport management, which was unable to control a fiasco caused by contractors hired by the airport builder Hansen Yuncken.

While Qantas and Virgin Blue have settled in to the airport, Rex passengers have complained since the first week.

The regional airline operates up to 31 flights in and out of Adelaide airport on weekdays, with a passenger flow of close to 900 people.

Rex represents 5 per cent of the airport's daily traffic.

Mr Breust said that using the old international terminal would solve complaints raised by passengers in hundreds of letters sent to Rex within days of the airline moving into the new terminal in early February.

Complaints included people having to walk almost 400m from check-in to the departure gate and a further 300m to planes along a poorly ventilated outbound walkway subject to extreme heat and flooding.

People also complained about having to pass through inbound security checks after arriving at the airport and a lack of buggies to carry elderly or sick passengers to gates.

Mr Breust said Rex would bring a special bus from Sydney that would transfer passengers from planes to the old terminal.

"For inbound passengers it will be great because you'll be out of the plane and on to the street very quickly," he said.

But the airline would continue to use the new terminal for outbound passengers, despite them having to walk about 800m.

"It's a process that's not done all at once: you check in, you walk to the gate and you sit down, then you walk further to the plane," Mr Breust said.

He said the airport had also promised to add windows, drainage and ventilation to the outbound walkway.

Adelaide airport's corporate affairs manager, John McArdle, told The Australian that the airport would not stand in the airline's way.

"If that is their preferred option, we will work with them to have the best outcomes for the passengers," Mr McArdle said.

But he said several issues needed to be resolved, such as security needs, baggage handling and the cost of upgrading the old terminal.

"We need to work out what's required by the (federal) Office of Transport Security, how Rex is going to handle baggage, do they need a carousel, how much that will cost ... and who's going to pick up that cost," he said.

Mr McArdle said that given that Easter fell this week, a move by the end of the month would be optimistic.