Aviation authorities in the UK continue to watch for developments in Iceland where planes are on high alert following a volcanic eruption.
Iceland closed airspace directly above Bardarbunga volcano yesterday after it began erupting under the ice of Europe's largest glacier following thousands of earthquakes over the past week.
The UK's air traffic control organisation NATS and safety regulator the Civil Aviation Authority said they were ready to take action if ash was detected spewing from the volcano.
A Virgin Atlantic spokesman said a flight from London Heathrow to San Francisco was rerouted away from the volcano as a "precautionary measure" but flights are now operating as normal.
In 2010 an eruption of the Eyjafjallajokull volcano, in the south of the Iceland, produced an ash cloud that caused a week of aviation chaos with more than 100,000 flights cancelled across the UK and the rest of the world.
A spokeswoman for NATS said: "NATS is monitoring the situation and working in close collaboration with the Met Office, Department for Transport and our safety regulator, the Civil Aviation Authority, as this dynamic situation develops further."
She added that NATS will help determine what impact the eruption will have for operations in UK airspace and advise airline customers accordingly.
A spokeswoman for the Met Office said: "We are in close contact with the Icelandic Met Office, but currently they tell us that the eruptions are sub-glacial, so no ash has made it to the surface.
"If ash does make it to the surface, we will run our model which will indicate where any ash would go, and we will inform the CAA and Nats. They will then make the decision on how that will affect any air flights."
Just minutes before the eruption, officials in Iceland raised the country's aviation alert to the highest level of red, which warns that an eruption could cause "significant emission of ash into the atmosphere."
However, scientists who flew over the ice cap yesterday afternoon saw no visible signs of the eruption on the surface.
Experts in Iceland's Met Office said it was not clear when, or if, the eruption would melt through the ice - which is between 330ft to 1,300ft thick - and fling steam and ash into the air.
A spokesman for budget airline easyJet said it is preparing to put contingency plans into action, using specialist technology to ensure any ash created by the eruption is detected and chartered.
"easyJet will use this and other data provided by the authorities to determine what, if any, changes it should make to its flying programme," he said.
Andrew McConnell, Flybe's director of communications, said: "We are monitoring the situation in Iceland very closely, currently there is no disruption to our services and all our flights are operating as normal. "
A Virgin Atlantic spokesman said one flight directed away from the volcano but that flights continue to operate as normal.
"Safety and security is always our top priority," he said.
Aviation chiefs are confident that the UK is much better prepared to deal with a potential ash cloud crisis than it was four years ago.
The Civil Aviation Authority said: "Volcanic ash can adversely affect aircraft in a number of ways. Jet aircraft engines in particular are susceptible to damage from volcanic ash.
"That's why there are comprehensive safety arrangements in place. As a result of the work that has been undertaken since the 2010 ash crisis and arrangements that have been put in place since, we are confident that high levels of public safety can be maintained, while minimising disruption."
The CAA said the improvements include i mprovements in observing and forecasting where ash is and its density - including a new radar in Iceland to detect ash in the atmosphere.
Two working groups including airlines and scientists have also been established to act as advisers on ash forecasting and how best to use the output from the Met Office modelling system.