NEW technology that could minimise future disruption to planes from volcanic ash was unveiled today by budget airline easyJet. The carrier will be the first airline to trial a new "weather radar for ash" system called AVOID (Airborne Volcanic Object Identifier and Detector).
The system involves placing infrared technology on to an aircraft to supply images to both the pilots and an airline's flight control centre.
These images will enable pilots to see an ash cloud up to 62 miles (100 kilometres) ahead of the aircraft and at altitudes between 5,000ft and 50,000ft.
This will allow pilots to make adjustments to the plane's flight path to avoid any ash cloud.
Millions of passengers had their travel plans wrecked when airlines had to scrap thousands of flights in recent weeks due to Icelandic volcanic ash.
Airports in parts of Scotland and Northern Ireland closed from 0700 BST because of risks from volcanic ash, the Civil Aviation Authority has said.
Glasgow, Prestwick and Derry are likely to be closed all day, while there are plans to shut Inverness in the morning only, and Belfast in the afternoon.
The CAA advised air passengers to check with airports before travelling and warned the situation was changeable.
Last month, volcanic ash clouds from Iceland grounded flights for six days.
The situation in the skies has been changing hour by hour, meaning the picture for air travellers is unclear.
Dublin Airport will also close from 1100 BST until further notice.
Forecasts show the 60 nautical mile buffer zone imposed around high concentrations of ash is close to some northern airports.
Belfast International 1300-1900
Belfast City 1300-1900
All times in BST. Source: CAA at 0200 BST
However, the latest advice issued by the CAA at 0200 BST said airports in Edinburgh and north-west England could safely stay open on Wednesday, despite the proximity of the ash.
The CAA says the South East of England is unlikely to be affected on Wednesday.
In a statement, the CAA said: "The situation remains changeable, so passengers expecting to travel from airports in Scotland, Northern Ireland, the North of England and north Wales should contact their airlines to check whether their flight is operating."
All flights in and out of Northern Ireland and the Irish Republic have been grounded since 0700 BST because of fresh risks from volcanic ash.
Airspace over Scotland's Outer Hebrides was closed, affecting Tiree, Barra and Benbecula airports, with Campeltown in Argyll also closed.
Flights in and out of the Republic are due to resume from 1300 BST.
An ash plume is drifting south from the same Icelandic volcano that wreaked havoc to European air travel in April.
Flights over Europe were banned for six days last month because of fears of the effect of volcanic ash on plane engines.
In the rest of the UK, schedules are operating as normal.
The decision to lift the restrictions followed safety tests that showed the engines could cope in areas of low density ash.
The fresh disruption comes as European Union transport ministers are meeting in Brussels to discuss ways to improve air traffic management in the wake of last month's events.
Last week a spokeswoman for EU Transport Commissioner Siim Kallas said that had there been more co-ordination at EU level, air traffic could have resumed up to three days earlier.
All UK airports have been given the go-ahead to reopen, the Transport Secretary Lord Adonis has said.
After six days of disruption due to a cloud of volcanic ash from an Icelandic volcano, airlines can now start a phased return to flight schedules.
The decision followed consultation with the Civil Aviation Authority and a reassessment of the risk to aircraft.
BAA, which operates many of the UK's airports, said people should contact their airlines before travelling.
"Not all flights will operate during the early period of opening, and we will do everything we can to support airlines and get people moving," a spokesman said.
Some restrictions will remain on flights in UK airspace, but they will be much less severe than before.
Dame Deirdre Hutton, of the Civil Aviation Authority (CAA), said there had been detailed consultation with experts to reassess the tolerance of planes to the ash cloud.
The CAA said it was a "situation without precedent" and that decisions had been made based on "thorough gathering of data and analysis".
"The major barrier to resuming flight has been understanding tolerance levels of aircraft to ash," the CAA said.
"Manufacturers have now agreed increased tolerance levels in low ash density areas."
Lord Adonis emphasised that safety remained paramount.
He said: "It is essential that we guarantee to the travelling public that the airlines are safe and that planes can safely fly."
Prime Minister Gordon Brown said: "This solution has been reached as a result of the close working between the government, the Civil Aviation Authority, airlines and the manufacturers, and will allow the thousands of UK citizens stranded abroad to return home to their families.
There will be plenty of time for a post mortem of what has happened
Willie Walsh, British Airways
"We will of course continue to monitor the situation closely; as we have said throughout safety is our primary concern," he added.
Shadow transport secretary Theresa Villiers said: "Labour must immediately commit to a full inquiry into this fiasco, which has caused so much travel misery and billions of pounds of economic damage.
"Six days into the crisis, we're suddenly told that there are actually levels of ash which are compatible with safe flying. The question angry passengers and airlines are already asking is why the government hadn't worked this out before the crisis occurred."
After the lifting of the restrictions, the first British Airways flight to touch down from Heathrow was a service already in the air from Vancouver, which landed shortly before 2200 BST.
The airline's chief executive Willie Walsh said he was pleased with the decision, but said it would take weeks to get back to normal levels of operation.
"We're now at British Airways going to start the difficult task of getting our stranded customers back home but I think this is an airlift that is unprecedented but we will make every effort to get our people back home."
He said "lessons can be learned" and added: "There will be plenty of time for a post-mortem of what has happened over the last few days."
He said parts of the UK airspace could have been opened several days ago. "My personal belief is that we could have safely continued operating for a period of time. I think there were occasions when the decision to close airspace could have been justified."
EasyJet said it planned to resume "some services across the UK and continental Europe from tomorrow morning," but added that the level of disruption meant it would be several days before the schedule returned to normal.
Flights have been grounded across the UK and much of Europe since Thursday following the eruption of Icelandic volcano Eyjafjallajokull.
The eruption sent vast amounts of ash into the atmosphere which poses a threat to aircraft jet engines.
Despite the lifting of the ban, it will be some time before flights return to normal.
The UK Border Agency warned people to expect queues as staff attempt to process large numbers of returning travellers.
A spokesman said: "We are manning as many passport desks as possible."
Some domestic flights are taking off in the UK, as airports begin to reopen after five days without flights because of the volcanic ash cloud from Iceland.
The first planes from Edinburgh and Glasgow both headed for Stornaway after 0700 BST - among a handful of internal flights scheduled from Scotland.
But Nats said a new ash cloud was causing uncertainty and there was now a worsening situation in some areas.
Belfast Airport said it hoped to start flights to Scotland from 1000 BST.
It said if it got the go ahead from Nats, a Flybe flight to Glasgow would leave at 1015 BST.
Although Scottish airspace is open most of the flights are said to be to destinations elsewhere in Scotland.
The first international flight from Glasgow is due to head for Reykjavik in Iceland at midday.
Schedules are constantly changing and passengers have been advised not to travel to airports until they have checked with their airline or tour operator.
At Glasgow, there was only a trickle of passengers checking in for the Stornoway flight, which carried about 30 passengers.
Some of the check-in desks were staffed, but had no queues. A flight from Aberdeen to Newcastle was set to depart at 0825 BST. Flights from Newcastle are expected to head to Aberdeen and the Isle of Man.