The volcanic ash cloud will ground all flights in UK airspace until at least 7am tomorrow, Nats said, in what is an unprecedented closure.
Nats, the air traffic control provider, said: "The cloud of volcanic ash is now spread across the UK and continuing to travel south. In line with international civil aviation policy, no flights other than agreed emergencies are currently permitted in UK controlled airspace."
The outfall from the volcano in Iceland has wreaked havoc across northern Europe, with Norway and Sweden already stopping flights, and Denmark on lockdown from 7pm this evening.
The band of ash is between 20,000 and 36,000 feet, the airspace in which most civilian flights cruise.
The effects of the national shutdown could be felt for days, as cancellations will have left aircraft and crew in the wrong place, as well as passengers.
A spokesperson for Flybe said: "There's going to be an issue in terms of rebooking passengers stranded abroad, and when we can get spare aircraft there to pick them up.
He said spare aircraft are likely not to be free until Saturday. "With the school holidays, flights down to the sun destinations are full."
Flybe cancelled all its flights today, which means 72 of its 73 aircraft are at their home base, ready to start operations again when the ash has cleared.
Flybe called this a "silver lining". "There will be very little knock on effect, because unlike the snow disruption back in February march, where aircraft were literally dotted all over Europe stuck, here nothing got off the ground this morning."
The spokesperson added that airlines will work together to get people to where they need to be. "We'll all be talking to each other about who's got spare seats, can we book people onto your flight. This is an area where the industry genuinely does come together."
Airlines are left counting the cost yet again, as the lock-down of UK airspace follows disruption caused by the worst winter for 30 years.
British Airways in particular, will be hit hard, as it had already lost an estimated £40-45 million during last month's industrial action.
www.flybe.com www.nats.co.uk