A report into an incident in which a plane landed at the wrong NI airport has said the air crew did not know there was another airfield in the area.
The plane landed at an Army base five miles away
The Eirjet flight in March 2006 should have touched down at City of Derry, but instead landed at a former RAF base at Ballykelly now used by the Army.
The 39 passengers and their bags were then taken by road to Londonderry.
An Air Accidents Investigation Branch report said the pilot did not have charts showing the approach to Derry.
The report says the crew of the Airbus A320 - operating on behalf of Ryanair - believed an instrument landing aid system at City of Derry was malfunctioning as what they saw of the runway did not match the instrument readings.
The report said that the 59-year-old captain said that once he saw Ballykelly, and not knowing there was another airfield in the vicinity, "his mind-set was that this must be his destination airfield".
They told the investigators that the presence of an instrument calibrating aircraft close by added to their belief that there was a technical fault.
Day late charts
The report also said an air traffic controller at City of Derry saw the aircraft and although he thought it "slightly low" he did not warn the crew about Ballykelly.
The controller told the investigators he may have had 30 seconds in which to alert the pilot but did not do so "because he incorrectly prioritised his attention in checking if the landing instruments were working".
The AAIB said that, before the flight, the captain had tried in vain to obtain a second set of charts showing the approach to Londonderry.
He got them a day after the incident and said that, had he seen them previously, he would have been fully aware of the existence of Ballykelly and would not have landed there.
Air traffic controllers had been told by the plane's crew: "We've just touched down," the report said
They were told they had landed at the wrong airport, to which the crew replied: "I know we have."