Germany is to shut down airports in the north of the country tomorrow morning because of the ash coming from an Icelandic volcano.
No flights will be allowed to take off or land at Bremen from 3am Irish time or Hamburg from 4am, German Air Safety (DFS) said in a statement late tonight.
The statement did not mention Hanover, which is also in the north.
It said Berlin's airports ‘may also be affected... through the course of the morning’.
However, both Aer Lingus and Ryanair expect to operate a full schedule tomorrow, with no volcanic ash-related disruption anticipated.
The Irish Aviation Authority has said there will be no restrictions in Irish airspace for at least 24 hours.
The IAA said all Irish airports will remain open but that a small number of European destinations may be affected, causing some disruption to flights to and from Ireland.
Intending passengers are advised to check with their airline before traveling.
The IAA is to give its next update at 9am tomorrow.
Earlier, Ryanair cancelled all flights to and from Scotland as airspace there has been closed due to the ash cloud from an Icelandic volcano that began to erupt on Saturday.
Aer Lingus cancelled 20 flights today to and from Irish airports to Scottish airports.
Ryanair said it strongly objected to the decision to close Glasgow Prestwick, Edinburgh and Aberdeen airports and believes there is no basis for the flight cancellations.
The airline said one of its planes has flown through a 'high ash concentration' zone above Scotland.
'No evidence of ash was encountered in flight or during a post flight inspection,' it said.
Ryanair said it would be meeting the IAA to have the restriction on its flights removed.
Meanwhile, Aer Arann flights between Dublin and Derry were also cancelled this morning.
Easyjet and Jet2.com have cancelled flights from Belfast International Airport.
The IAA says while Irish airspace is still open, a change in wind direction tomorrow may cause further more extensive disruption.
Eurocontrol, the organisation responsible for the Safety of Air Navigation in Europe, says that about 500 flights will have been cancelled by the end of the day due to the ash cloud.
Passengers planning to travel by air over the coming days are advised to regularly check their airline's website and the IAA website in advance of going to the airport.
Passengers should also check the status of their destination airport.
The Irish Travel Agents Association has advised passengers affected by flight cancellations to contact their travel agents.
The ITAA said customers should not turn up to airports unless they are told to do so.
The majority of customers using travel agents to book flights to and from Scotland are business people.
ITAA President Pat Dawson has said they are monitoring the situation.
Iceland's most active volcano, Grimsvotn, started erupting on Saturday, sending a plume of white smoke miles high into the air.