The sabre-rattling by Irish PM Leo Varadkar that in the event of a no deal Brexit Ireland might block off UK access to Irish airspace is pathetic. Treaties dating back to the beginning of the International Air Services Transit Agreement signed as part of the Chicago Convention in 1944 guarantee the freedom of the skies. This is signed by 133 countries, including the UK and all EU member states. Ireland has been a signatory since 1957.
There is another agreement permitting British aircraft to fly over Ireland which the Irish government chooses not to publicise. The Irish Department of Defence and Department of Foreign Affairs with the Irish Aviation Authority (IAA) have entered into a bilateral agreement with their British counterparts: the RAF, the Civil Aviation Authority, the Ministry of Defence, and the Foreign and Commonwealth Office that in the event of a terrorist hijacking, RAF jets would be scrambled to defend Ireland. Neutral Ireland has no supersonic military aircraft capability.
Presumably this bilateral agreement permitting the RAF to conduct armed operations in Irish-controlled airspace in the event of a real-time or envisaged threat of a terrorist-related attack over the skies of Ireland, will not be torn up after Brexit. The Irish are Britain’s kith and kin, it is inconceivable that Brexit Britain would not come to their aid in the event of an Aer Lingus transatlantic flight being hijacked mid-Atlantic. Varadkar is bluffing for domestic consumption.