Opened quietly last October, the Wirraway museum is a bit of a misnomer as it showcases a variety of fascinating warbirds, including even some with metal patches denoting old bullet holes. Entry is free.

But it's the lone CAC Wirraway, a World War II training aircraft which is the real star of the show here for site owner and famous Hunter Valley airshow operator Paul Bennet. And it's a very rare relic, said to be one of only three still flying in Australia out of more than 700 built.

In its drab green livery, the legendary Wirraway (an Aboriginal word meaning 'challenge') is unobtrusive within the museum's hangar, hidden between three other aircraft while two other magnificent warbirds stand outside.

And yet, looks are deceiving. The WWII trainer (1939-1946) is credited with being the foundation of Australian aircraft manufacturing. It was the first aeroplane made by the Commonwealth Aircraft Corporation (CAC). Later it was modified into a wartime 'emergency fighter' known as the Boomerang.

Yet, as painted up here to resemble Wirraway A20-176, it instantly recalls its fame as Australia's unlikeliest fighter, for "doing the impossible": a humble pilot trainer which, despite the odds, surprised and shot down a vastly superior Japanese 'Zero' enemy aircraft near Buna, New Guinea, in 1942. It was an amazing feat as the Wirraway was used only for reconnaissance missions. It was never intended as a frontline combat aircraft even in those desperate early war days.

The enemy aircraft shot down was actually a Nakajima aircraft of the Imperial Japanese Army/Air Force, but an impressed US General Douglas MacArthur awarded Aussie pilot Jack Archer with a Silver Star for combat valour (and surviving).

"Better still, Archer and his observer were then also given 12 bottles of beer by the Australian High Command as a reward. Six they drank and the others they sold," Wirraway museum curator John Benson told Weekender with a laugh.

"Some 755 Wirraways were built as pilot trainers and general purpose aircraft. Of these, only 15 are now registered. Only five are airworthy, with three being worked on and the rest are static, including one in storage in Florida. But only three are flying at present and we have one.

"It's one of Paul's favourite aircraft but the others we have on display are all great too."

All beautifully restored, the warbirds include a Curtiss P-40E Kittyhawk and a red-nosed North American T-28 Trojan trainer deployed as a counter-insurgency aircraft during the 1960s Vietnam war.

Parked outside the hangar is another strange beast. It's the graceful, if gaudy (painted bright yellow), Yak -52 Soviet aircraft whose design dates from 1976. It was used to train Russian pilots for MIG jets.

Nearby, with its unique folded wings, as it would travel on a US aircraft carrier, is the yellow-tipped, black Grumman Avenger dating from 1942. It was created initially for the US Navy. One WWII Avenger pilot rescued in 1944 later became US President George H.W.Bush.

"It became the biggest single-engine torpedo bomber the Allies had. It was developed in the wake of the Japanese attack on Pearl Harbour in December 1941. That's why it was called the Avenger," Benson said.

"Six Avengers took part in WWII's Battle of Midway. Five were shot down and one came back, badly damaged," he said.

Missing on the day Weekender visited, however, another WWII veteran, a twin-engine Beechcraft Model 18, which was in Rutherford. In the postwar era, the light bomber and photo-reconnaissance aircraft went on to become the preferred aircraft of businessmen.

The Beech 18 closely resembles the aircraft that aviator Amelia Earhart was flying when she disappeared over the Pacific in 1937.

One thing missing from the exhibition, however, is any WWI era biplanes.

"That's because that type were mainly used as trainers, while most of our planes are warbirds, which saw actual war service," the museum curator said.

With such an intriguing collection on display (and for adventure flights), it's little wonder the Hunter Valley Airshow (shifted to Pokolbin temporarily from Scone in April) attracted 15,000 visitors over two days.

But only about 500 people have officially visited the Wirraway Aviation Museum since it opened nine months ago.

"We haven't been seeking publicity," Benson said. "Eventually we'd like to erect a major two-storey aviation centre, a flying museum, on the (adjacent) vacant paddock."

Perhaps the biggest surprise inside the aviation hanger, however, is not really advertised. Liked the historic Wirraway nearby, a Cessna 02 seems like an overlooked artefact.

Used as a forward control aircraft in Vietnam, the 1967 warhorse looks squat and ungainly with two engines, one at front and one at the rear to make sure it kept flying straight even under heavy enemy fire because of its priceless radio equipment onboard.

"It's the one I like the best. It's the same search plane used in the 1988 movie Bat 21, about a pilot rescue in the Vietnam war. The movie starred Danny Glover and Gene Hackman," Benson said.

"In Danny Glover's later book, he wrote that he spent more time in this aircraft with the real pilot than he did with co-star Gene Hackman.

"Ours is a two-seater at present, but in time this will be changed to accommodate three passengers. The original radios in the back weren't standard. You had to have CIA clearance. They could contact US ships at sea, talk to the marines, the army or Australian forces.

"It's my favourite aircraft. Paul doesn't understand. Unless you've seen the film Bat 21 it means nothing. Visitors say, 'What is that?' It's not what you'd perceive as a fighter where it is now, but it carried rockets, bombs and smoke bombs and has old bullet holes in it, here and here and at back," Benson said.

To reach the aviation musum from Cessnock Aerodrome, tourists must drive in a virtual U-shape: up Broke Road, then down De Beyers Road, then turn left to the very end of Grady Road.