The Republic of Ireland's limited air defence system acquired after the 9/11 attacks in 2001 is being beefed up with orders for more ammunition to counter aerial threats.
But 10 years after the attacks which stunned the world the country still has no means of intercepting a hijacked airliner with the government relying on Britain to come to assist.
Acquiring jet interceptors has been ruled out on cost grounds and the the low level threat from terrorism.
The Republic's only defence, apart from intelligence co-operation, relies on short range anti-aircraft guns and surface-to-air missiles to defend point targets such as Dublin Airport.
Now the army is to acquire 5,000 rounds of 40mm ammunition for the guns called HE-T, or high explosive tracer rounds.
A 2003 Defence Forces annual report pointed out that "the lack of air intercept capability has been identified and is under consideration".
However, that concern was dropped from subsequent reports.
The cost of modern fighter aircraft, such as the Swedish SAAB Gripen and the French Dassault Rafale, at around $65m (€48.5m) each or the Eurofighter Typhoon at over $100m each, rules out Ireland acquiring modern air defences. But aviation sources said that, with most air forces downsizing, second-hand jets could cost less.