A volcanic ash cloud forced British air traffic authorities to close the airspace above Scotland and Northern Ireland as of Wednesday morning, only hours after a similar flight ban was lifted.

No take-offs and landings will be allowed as of 0600 GMT Wednesday, Britain’s Civil Aviation Authority (CAA) said late Tuesday. The CAA said it feared the situation to deteriorate in the course of Wednesday, as the ash cloud was expected to move south towards England and Wales.

In Ireland, flights from northern airports are suspended until further notice as of 0600 GMT, from Dublin as of 0900 GMT. Restrictions are also likely to be imposed at airports in the south of the country in the afternoon, the Irish Aviation Authority said.

Ash from the volcano at Iceland’s Eyjafjallajoekull glacier caused authorities to impose no-fly zones above Ireland, Scotland and Northern Ireland from Monday to Tuesday noon. Hundreds of flights had to be cancelled.

European airspace was shut down for six days last month, stranding hundreds of thousands of passengers and leading to billions of dollars worth of losses for airlines and industries.

Following the closures, Britain, together with leading aircraft manufacturers, put in place upper limits for airborne ash concentration.

“Met Office forecasts show that levels of ash in the atmosphere over Scotland and Northern Ireland will exceed the concentrations that engine manufactures have agreed are safe for operations,” a CAA spokesman said of Wednesday’s bans.

At a meeting Tuesday, the European Union transport ministers agreed the EU should immediately create an air-traffic crisis group to ensure member states coordinate reactions to any future threats to airspace.