Europe's skies reopened for business on Wednesday but it could take days or weeks to clear the six-day backlog.
Here is a list of countries as of 1030 GMT on Wednesday and their airspace status:
AUSTRIA - Airspace open as of 0300 GMT Monday.
BELGIUM - Belgium began allowing planes to land on Tuesday. Some flight departures were allowed from 1200 GMT Tuesday.
BOSNIA - Airports open (see Serbia entry).
BRITAIN - Britain reopened its airspace on Tuesday night. British Airways say it will operate all its long-haul flights departing from Heathrow and Gatwick airports on Wednesday, but there would be short-haul cancellations to and from London airports until 1200 GMT.
BULGARIA - All airspace and airports open.
CZECH REPUBLIC - Airspace and airports open as of 1000 GMT on Monday. Prague Airport plans to handle 322 flights on Wednesday, around 83 percent of normal operations.
DENMARK - Denmark will reopen all its airspace at 0900 GMT.
ESTONIA - Airspace open.
FINLAND - Finland's airspace is open and most airports will operate from 0900 GMT.
FRANCE - Air traffic is recovering, with Air France-KLM resuming all of its long-haul flights and around two-thirds of its mid-haul flights.
GERMANY - Air traffic control say German airspace would be open by 0900 GMT. Airports in the cities of Hamburg, Berlin, Bremen, and Hanover were open at the moment, but all others, including the main traffic hub in Frankfurt, remained closed. No fixed time had been set for the full opening of German airspace.
HUNGARY - Hungarian airspace is fully open, the air traffic authority said around 0800 GMT on Tuesday.
IRELAND - Irish Aviation Authority says airspace is open all over Ireland. Aer Lingus say that all UK and European flights scheduled to depart up to 1300 (1200 GMT) on Wednesday have been cancelled but that all flights after 1200 GMT are scheduled to operate.
ITALY - Airspace has completely reopened.
LATVIA - Airspace open.
LUXEMBOURG - Luxembourg Airport reopened at 0800 GMT Tuesday.
MOLDOVA - Resumed international flights from 0730 GMT Tuesday.
MONTENEGRO - Airports open (see Serbia).
NETHERLANDS - Passenger flights began on Monday. Night flights resumed on Tuesday.
NORWAY - All Norway's airspace, including over offshore oil installations, is open until 1200 GMT. Airport authority Avinor anticipates that the airspace will remain open until tonight.
POLAND - Poland was reopening its airspace from 0500 GMT.
ROMANIA - Airspace fully reopened.
RUSSIA - All airports open. Aeroflot is flying to the United States via the North Pole.
SERBIA - Air traffic control said most of the air space in its area of responsibility (Serbia, Montenegro, parts of Bosnia and Southern Adriatic) is again affected by the volcanic ash cloud. It will decide every six hours whether to close airspace partially or completely. Airports in Serbia, Montenegro and Bosnia are currently open for traffic.
SLOVAKIA - Airspace and airports open as of 1240 GMT on Monday. Bratislava airport has resumed operation of flights, but no heavy traffic as Ryanair, operating most of the flight to and from Slovakia, has suspended all flights until Thursday 1100 GMT.
SLOVENIA - Slovenian airspace was opened at 1000 GMT on Tuesday. It had been partly closed since 0200 GMT Tuesday.
SPAIN - 17 airports open.
SWEDEN - Stockholm Arlanda airport will reopen at 1400 GMT. Aviation authority say bans on flying through most of Swedish airspace would be gradually lifted throughout the day.
SWITZERLAND - Geneva and Zurich airports reopened on Tuesday morning though some flights were cancelled at both.
TURKEY - All airports open. Planes flying out of the Black Sea cities of Samsun, Sinop and Zonguldak have been advised not to fly higher than 6,000 metres.
UKRAINE - Major airline MAU say it plans to conduct all regular flights, including flights to Europe.
