UK and Irish airspace is set to close from 12:00 as a result of the ash cloud from an Icelandic volcano which is spreading over northern Europe.
The ash originates from a volcano beneath the Eyjafjallajokull glacier in southwest Iceland.
Iceland's coast guard has been monitoring the eruption with a specially-equipped Bombardier Q300 surveillance aircraft which has captured images of the volcanic plume breaking the cloud layer.
© Icelandic Coast Guard
All air traffic in the UK and much of Ireland will be halted. London Heathrow's NOTAM service has issued an advisory that the airport is available only as a diversion destination for emergency traffic.
London Gatwick has similarly states that its capacity for diversion is "reduced" and airlines are "advised to make alternative arrangements".
Air navigation service provider NATS states that no flights, unless in emergency, will be permitted in UK-controlled airspace from 12:00 until at least 18:00.
"This has been applied in accordance with international civil aviation policy," it says.
British Airways says it will not operate any flights from the UK from 11:30, adding that some services have already been scrapped.
BMI has similarly abandoned its schedule today. Regional carrier Flybe has operated just 11 of its 565 planned flights, with all remaining services axed.
Budget carrier Ryanair stopped services at 09:00 and EasyJet has advised of similar disruption.
Source: London Volcanic Ash Advisory Centre
Volcanic ash movement is tracked by nine advisory centres worldwide. The London centre monitors ash over the UK, Iceland and the northern Atlantic Ocean.
"Although this is a relatively small area it covers some of the busiest airways in the world," says the centre, adding that an Icelandic eruption is capable of affecting a large section of airspace in a short time.
The Irish Aviation Authority, following advice from the centre, will start to close sections of Irish airspace from 12:00 today.
"This will result in the shutdown of operations at Dublin Airport," it says. Aer Lingus says it has been advised to expect closure of Irish airspace until 20:00.