The cost of the government jet was causing concern to the Department of Finance in 1983 but there was strong support among ministers for its retention. They argued it had advantages, including security and flexibility, “on which no monetary value can be placed”.

A memorandum for government dated June 21st, 1983 showed it had cost £2.5 million in 1980. During 1982, the year covered by the study, the jet carried 686 passengers on 204 flights to 23 different destinations, the most popular being Brussels.

It listed 10 advantages of the jet, including security, flexibility and availability in “times of crisis”, as well as the fact that all European Economic Community states had similar transport, bar Luxembourg and Greece. The Department of the Taoiseach wanted it retained and said it was “clearly in the national interest” and “outweighed the evaluation of the services purely on cost grounds”.

The Department of Finance, however, was not so sure. The memo said it thought the advantages listed were “open to question”. “The very high cost of the jet and the very low level of its utilisation by ministers are a cause of great concern to the Department of Finance,” it said.

The department suggested ministers use scheduled services or an air-charter service. It said the jet was regarded as “a very expensive and luxurious facility” and the “overall effect on public morale of a decision to retain the government jet should also be considered”.

But minister for transport Jim Mitchell believed the jet was “a normal requisite for the conduct of international business”.

At a government meeting in July, it was decided “the question of a better return from the investment in the jet” should be considered.

Another file from the Department of the Taoiseach shows that when British prime minister Margaret Thatcher visited Ireland, the British delegation refused to travel in an Air Corps helicopter.

A bill from Irish Helicopters on the department’s file charged more than £8,000 for the hire of two helicopters for the visit in December 1980. An attached note explained they were chartered because “the single-engined helicopters of the Air Corps were not acceptable to the British for fear of engine failure”.