An electronic aid at Cork Airport which helps pilots land in bad weather will not be available for several weeks.
The Instrument Landing System (ILS) is set for an upgrade but, because the airport is prone to bad weather, the work must be completed during the summer periods, the airport's busiest.
The ILS sends an electronic beam into the air from the runway. Aircraft lock on to this several miles from the airport and follow it to their touchdown point. In effect it is a pilot's eyes at times of low visibility, particularly during fog.
It is the first of a number of planned ILS replacement works at the State's main airports in the next three years.
A spokesman for the Irish Aviation Authority yesterday gave assurances that passengers were not in danger.
"Pilots using modern aircraft will have a range of other navigational aids to guide them on to the runway," he said.
"We chose Cork Airport first because it is the most hostile environment. It is located at 530 feet, whereas the others are at sea level.
Work on the replacement of the 13-year-old ILS used for aircraft approaching runway 35 from the north over the city will begin in June.
It will involve the placing of larger concrete plinths at the southern end of runway 17 for the installation of a bigger aerial array. The replacement should be switched on in August.