Up to 200 people were expected to be stranded in London hotels for Christmas because of flight cancellations and delays at Heathrow.
The airport cancelled 64 flights on Monday, because planes and crew were in the wrong airports after fog led to 86 flights being cancelled on Sunday.
Gatwick, London city and Stansted Airports have also been disrupted.
Greg Ward, the Operations Director of the British Airport Authority at Heathrow said every thing possible was being done to help passengers.
While there were some delays at Irish airports on Sunday night, flights were landing and taking off on schedule on Monday.
Up to 45,000 people were expected to pass through the airport on Monday but a spokesperson said it was quieter than usual for Christmas Eve.
Four Dublin-bound flights were cancelled on Sunday and on Monday morning there were some delays to flights.
Dublin Airport stayed open until 2.30am on Sunday night to cope with the backlog.
