They were the self-proclaimed "secret soldiers of the Cold War", flying covert missions for the United States' government, using rags and coffee cans to light runways for moonlit landings and attracting "lovely, friendly, curious lassies" at every airport.

The Central Intelligence Agency's (CIA) secret airline flew covert missions to fight communism in China, Vietnam and Korea in the 1950s and 60s, but newly released US files reveal the airline also operated in New Zealand to help break the 1951 Wellington waterfront dispute.

Civil Air Transport (CAT) is called "the world's most shot-at airline" by veterans and was secretly owned by the CIA. It ran passenger and cargo services as a cover for secret missions from 1950 to 1968.

Deregistered watersiders and others at the corner of Queen and Customs Sts being moved from the waterfront area by police on 28 May, 1951.

The new CIA files, published online with 13 million other documents in January, reveal a Kiwi mission called "Operation Railhead".

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The airline was contracted by the New Zealand Government to fly about 8000 tonnes of "everything from brewery malt to racehorses" more than 150,000 kilometres in 1300 crossings of the Cook Strait from May to June 1951.

ALEXANDER TURNBULL LIBRARY Union marchers clash with police at the intersection of Cuba St and Dixon St in Wellington on May 3, 1951.

The US provided four Curtiss C-46 Commando planes and crew to fly cargo between Paraparaumu Airport near Wellington to Woodbourne in Blenheim on the South Island.

It was chartered to ensure that goods could still be shipped around New Zealand during the waterfront dispute of 1951. The pay dispute was the largest industrial confrontation in New Zealand history bringing the nation's ports to a standstill and, at its peak, taking 22,000 workers off the job from February to July 1951.

Left-leaning political commentator Chris Trotter said the secret Kiwi mission was a revelation.

"It is an important historical detail because it shows how real the ideological battle was and it shows that a lot of the fears on the left have some real basis in fact.

"There was always a suspicion that the US was manipulating events from behind fronts. This detail reinforces all the worse fears of the people involved in the dispute."

Historian Anna Green, who wrote a book about the waterfront dispute, was not aware of the CIA involvement.

"I didn't come across any reference to that at the time. It doesn't surprise me. There was a strong sense from the people I interviewed that the government was involved in various activities to try and break the strike," she said.

The CIA report on CAT's Kiwi mission states the the US airmen mixed well with New Zealanders.

"Outstanding features of this charter operation were the extraordinarily warm relationship that developed between CAT personnel and the New Zealand people," the CIA report states.

A history of the airline on a website for CAT veterans also talks of warm relations with the locals.

"Dependability and an on-time record endeared us to the Kiwis. Local families insisted on tossing our laundry in with their home washing instead of taking it to a commercial place," the website states.

"Lovely, friendly, curious lassies in uniforms of the Royal New Zealand Air Force visited Woodbourne Aerodrome."

The history also details how they landed at Woodbourne at night without runway lights.

"Our Southern Island home was Woodbourne Aerodrome, a grass field without boundary markers or lights ... We reverted to coffee cans, rags and oil."

A 1949 CIA document declassified in 2013 shows the US mission may have been motivated by communist fears. The report claimed that the main communist influence in New Zealand came from trade unions.

"Communists or Communist sympathisers in key union posts were strongest in the Waterside Workers Union," the report states.

The New Zealand Waterside Workers' Union was forced to break into smaller unions for each port after the dispute ended in June.

Historian Dick Scott's 1952 book about the dispute, 151 Days, noted the flights and claimed they were part of US support for the New Zealand Government during the confrontation. The flights were reported in local media at the time, but Kiwis would not have been aware that the airline was secretly owned by the CIA.