A Boeing E3 Sentry
A US spy plane spent several hours over Ireland earlier this week, prompting questions as to the nature of such clandestine surveillance flights.
The plane's erratic behaviour was spotted by a Newstalk listener on the popular app, Plane Finder.
It flew over Dublin to Shannon to Cork, and then back to Dublin again in a triangular formation for approximately five hours.
The plane's transponder - which sends information to receivers on the ground or in the ocean – initially showed it to be a Boeing E6 Mercury.However, it is now believed to have been a Boeing E3 Sentry aircraft.
The Irish Aviation Authority (IAA) confirmed the flight, and said that: "A US military aircraft, with a pre-filed flight plan, operated in Irish airspace on Tuesday with approval from the Department of Foreign Affairs ."
The aircraft remained at around 28,000 feet throughout the five-hour period, and stayed over land the majority of the time.
The Department of Foreign Affairs said: "Under long-standing arrangements we permit US military aircraft to overfly Ireland without seeking prior permission provided they are unarmed, carry only cargo and comply with navigational requirements".
The US embassy in Dublin said: "The US government is appreciative of the Irish Government's policy of granting permission on a case by case basis for the transit of U.S. service members and aircraft through Ireland".
"The US government appreciates and respects the conditions under which planes can utilize Irish airspace in accordance with Irish law".
It is believed 13 such clandestine flights occurred over Ireland during the month of August.
Speaking to Newstalk Lunchtime, security analyst Dr Tom Clonan said the most likely explanation for the flight was that, "[Ireland] has had other visitors to our airspace in recent times.
"It could have been a training flight...it could have been because maybe US VIP flights passing through our controlled airspace or - and I think this is probably the most likely explanation - we have had other visitors to our airspace in recent times.
"We had Russian aircraft bombers enter our controlled airspace recently down the west coast...and in the last number of years, with the Ukraine and rising tensions in the Balkans, some of the old Cold War rhetoric has found its way back into the international foreign relations narrative".
A Boeing E3 Sentry aircraft, according to the United States Air Force, is used an all-weather surveillance, command, control and communications vehicle.