Years of work and countless hours of restoration will culminate in the launch of a new vintage plane display at a museum in outback Queensland this weekend.

The restored 1944 Catalina "flying boat" will be unveiled at the Qantas Founders Museum in Longreach.

The rare plane was purchased by the museum in Spain in 2009 as an example of the type of aircraft Qantas pilots flew during World War II.

It had been used in Spain as a water bomber, but needed a massive restoration job before it could be flown back to western Queensland in 2011.

Since then, the plane has been restored and painted in wartime camouflage and as of this weekend will be open for tourists to view.

Museum chief executive Tony Martin said there had been many challenges along the way, including mechanical troubles with the plane and fuel issues on the journey home.

The Catalina spent about 18 months at a military base in Thailand after it broke down in transit.

Mr Martin said a large team of volunteers and staff had helped bring the project to fruition.

Mr Martin said the Catalina restoration cost more than $1 million. ( ABC News: Chrissy Arthur )

"There are so few of these aircraft around the world," he said.

"It is wonderful to see a project conclude - we have had blood, sweat and tears, literally, over this aircraft.

"But at the end of the day, everyone is focused on the story it tells, the really important story about those brave pilots that operated them during the Second World War."

The Catalinas were used during WWII on top secret "Double Sunrise" flights from Perth to Ceylon.

Qantas pilots flew the planes to keep supply lines open between Australia and England, breaking the Japanese blockade over the Indian Ocean when Singapore fell.

"They still hold the world record for the longest flight - it is something like 33 hours continuous flying - and nobody knew about them," Mr Martin said.

"Even the Qantas crews that operated them, they had to be top secret.

"These missions they were flying were so dangerous, they were flying over Japanese occupied waters and had they been shot down, they would have been executed."

Catalinas were used for top secret flights to Ceylon in World War II. ( Supplied: Qantas Founders Museum )

Mr Martin said the restoration project had been a costly exercise but he hoped it would increase museum visitor numbers by 10 to 15 per cent.

"It would not have been possible without a philanthropic trust - the John Villiers Trust Fund, which gave us $300,000," he said.

"The whole project is actually in excess of about a million dollars."

Mr Martin said the sounds of the engines starting and the plane taking off had been recorded during the Catalina's flight home, and that audio had become part of the display.

"What you do is you sit in that aircraft, you are told a little bit about the significance of the aircraft, and then you will actually experience it," he said.

"So the aircraft comes alive, your seats vibrate. It's quite loud in there because it is authentic sound."

The museum said it had decided the plane would not fly again.

"The museum has a no-fly policy, because it is a risk we don't wish to undertake," Mr Martin said.

"To keep aircraft like that flying, you are probably looking at $2,000 - $3,000 an hour just to maintain them, so it is a budget we probably can't come to."