Flights out of Dublin airport were disrupted this morning after a power cut.
The terminal building was thrown into darkness shortly before 8am, and back-up generators failed to restore electricity.
A Dublin Airport Authority spokesman said there would be minor delays to outbound flights throughout the morning.
A fault with an internal circuit breaker was blamed for the half-hour long cut. Hundreds of passengers waiting for flights cheered when the lights came back on.
The ESB said the power cut was an airport problem but that repair crews were being sent to the nearby electricity sub-station to check power supplies in the north of the city.
Fine Gael transport spokesman Fergus O'Dowd called for an independent audit into the power cut.
"Dublin airport was effectively shut down for 40 minutes due to an internal power cut," he said. "This is an unacceptable development at the country's largest airport and the main gateway to the rest of the world.
"It is disturbing from a health and safety point of view that the airport could be left without power for any period without access to an adequate back-up supply," he said.
Ryanair head of communications Peter Sherrard said thousands of passengers had been "inconvenienced by the Dublin airport monopoly's incompetence".
"Will the DAA monopoly now compensate these passengers and airlines because of their failure to provide an adequate contingency plan?" he asked.