Flights in and out of Ireland could be delayed or cancelled until well into next week.
Yesterday, a massive technical failure left Britain's Air Traffic Control unable to function for a number of hours.
The fault has since been resolved but more than 600 flights to Britain were cancelled and it could take some time before the backlog is cleared.
“Can you imagine [a flight] maybe that’s departed from here [Britain] to go somewhere like the Canary Islands?” former pilot Terry Tozer said.
“They’re going to run out of hours before they can come back but there probably won’t be a crew there to replace them.
“This is going to have massive knock-on impacts on every airline’s schedule.”
Britain’s National Air Traffic Services suggested anyone travelling today check the status of their flights with their airline before they depart for the airport.
One group of holidaymakers in Gran Canaria were left stranded at the airport after their Ryanair flight to Edinburgh was cancelled.
Some 300 travellers were told the next direct flight would be the following week and there was “zero chance” of an emergency flight being arranged for them.
Many were forced to sleep at the airport that night as so much of the island’s accommodation had already been booked out.
Passengers have been told they can rebook themselves onto alternative flights out of the island but prices have “skyrocketed” since the technical glitch.
"I don't believe they can't do another flight," 19-year-old student Marco McCool told Sky News.
"We have been stranded with no options. We are students so we have not got the kind of money to book another flight.
"We have literally just been left to fend for ourselves."
Ryanair’s website states that compensation may be refused to passengers if a flight is cancelled because if the cancellation is caused by "extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken by Ryanair".
Speaking to journalists, Michael O'Leary said he hoped normal service could resume tomorrow.
“We’re looking to run a couple of additional extra flights today - rescue flights,” he said.
“It’s very difficult because we’re also tight on crews, we’re also tight on aircraft.
“We hope by the end of the day, Tuesday, that we’ll be running a normal operation.”
Main image: A traveller in Dublin Airport. Picture by: RollingNews.ie