The cloud of high density volcanic ash has moved northwest, allowing European airports to reopen.
Airports in the UK, Italy, France, Spain, Portugal and Germany were affected over the weekend.
Passengers on transatlantic services continue to see delays, however, as the ash above the North Atlantic Ocean means flights are having to be rerouted.
Airports on the Iberian peninsula may be forced to close this afternoon.
Forecasts show an area of higher ash concentration, currently off the coastline in the area, could move in a north-easterly direction from the Atlantic.
Around 28,500 flights are expected to operate today, which is about 500 below an average Monday for the time of year, said Eurocontrol, the European Organisation for the Safety of Air Navigation.