The CAA has lifted the no-fly zone that has been affecting flights at Heathrow and Gatwick this morning, according to Nats.
The decision followed information from the Met Office about the nature and location of the ash cloud.
A no-fly zone remains in place in two areas affecting operations in Northern Ireland and the Shetland Isles.
Airports falling within the no-fly zones include Belfast City, Londonderry, Shetland and Orkney. All other airports are open.
The volcanic ash cloud no-fly zone in the UK was extended to cover airports in England, Scotland and Wales overnight, causing further serious disruption to services.
Gatwick airport was due to be closed for arrivals until 1pm and there was disruption at Heathrow, although airports in the north of England and the Midlands including Manchester and Birmingham were re-opened after closures yesterday.
The dense area of ash cloud is moving south and east and closures have been reported in mainlaind Europe, with Amsterdam’s Schipol among airports affected.
The closures in UK airpsace came after advice from the air traffic authority Nats and the CAA that the ash cloud posed a danger to aircraft.
However, Virgin Atlantic chairman Richard Branson labelled the closure of Manchester a “joke” and questioned the scientific basis on which Nats is making its recommendations.
Over the weekend the ash cloud closed airports in Northern Ireland, Wales, Northern England ans Scotland. According to the Met office the current disruption is only due to last a few days until the winds divert the ash away from UK airspace.
Airports currently in the no-fly zone include those in Northern Ireland, Ronaldsway, Edinburgh, Aberdeen, Inverness and Northern Scotland, Cardiff, Swansea, Bristol and Farnborough.
Rail companies including Virgin Trains and Eurotunnel are putting on additional services to try to get people to airports that remain open.