Flights across the UK were today ( April 16) banned for the second day because of the ash cloud from an Icelandic volcano.
The British air traffic control body, NATS, said than the grounding of flights in the UK would last at least until 1am on Saturday.
But the body has allowed a few flights in and out of Northern Ireland and western Scotland.
A statement by NATS said: "The cloud of volcanic ash continues to cover much of the UK and the eruption in Iceland continues.
"Following a review of the latest Met Office information, NATS advises that restrictions preventing flights in English controlled airspace will remain in place until 0100 (UK time) tomorrow, Saturday 17 April, at the earliest.
"Flights in Northern Ireland and the Western Isles of Scotland to and from Glasgow and Prestwick will continue to be allowed until 1900 (UK time) subject to individual co-ordination.
"North Atlantic traffic to and from Glasgow, Prestwick and Belfast may also be allowed in this period.
"From 1900 (UK time), forecasts indicate that Scottish airspace may be able to accept domestic flights within Scotland and Northern/Southern Ireland, and North Atlantic flights to/from airports in Scotland and Northern Ireland.
"We will review further Met Office information and at 1430 (UK time) we will advise further arrangements. In general, the situation is dynamic and subject to change.
"We continue to work closely with airports, airlines, and the rest of Europe to understand and mitigate the implications of the volcanic eruption."
The ban is expected to hit thousands of flights with the travel plans of hundreds of thousands of travellers, including many on business, disrupted.
Heathrow Airport said it had cancelled 1,250 flights today, affecting 180,000 passengers.
Yesterday it cancelled 899 flights.
Gatwick Airport said 730 flights would be cancelled today, affecting 90,000 passengers.
The airport cancelled 511 flights yesterday.
Many travellers are switching to rail with Eurostar yesterday reporting an increase of 10,000 in bookings on its cross channel services to Paris and Brussels.
Authorities in Ireland, France, Germany, Norway, Sweden, Denmark, Finland, Belgium and the Netherlands have closed all or parts of their air space.
Eurocontrol, the European air traffic control body, warned that disruption could last over the weekend.
There were also fears that countries further east, including Poland and the Czech Republic could be hit by the ash cloud tomorrow.
Lord Adonis, the UK transport secretary was today meeting with senior transport executives to see what contingency plans might be needed if the situation continues.
The ash is from the Eyjafjallajoekull volcano in south east Iceland.
Aviation experts have warned that particles of rock, glass and sand in the ash cloud could jam airline engines.
All four engines on a BA plane shut down when it flew into an ash cloud over Indonesia in 1982. The plane landed safety after the pilots got the engines to restart.
www.baa.com www.nats.co.uk www.eurocontrol.int www.gatwickairport.com