A NEW volcanic ash cloud created after the Icelandic volcano eruption "strengthened" could delay more flights in the UK it has been reported.
Air traffic control company Nats said the "situation is variable".
But it said Scottish airports should be available from 7am today and other airspace over England from 1pm, although not including the main London airports.
Nats said in an update shortly before 3am today: "Since our last statement at 9pm yesterday, the volcano eruption in Iceland has strengthened and a new ash cloud is spreading south and east towards the UK.
"This demonstrates the dynamic and rapidly changing conditions in which we are working.
"Latest information from the Met Office shows that the situation is variable.
"The information shows that Scottish airports should be available from 7am and more airspace over England may become available from 1pm although not as far south as the main London airports."
Nats said it would provide further updates at around 9am today.
Earlier, Prime Minister Gordon Brown announced plans to use Royal Navy vessels to bring home some of the estimated 150,000 Britons stranded abroad.
A brand new £500-million cruise ship, the Celebrity Eclipse, is due to leave Southampton tonight for Bilbao to pick up around 2,000 British tourists from the northern Spanish port.
A meeting of emergency planning committee Cobra, chaired by Mr Brown, was held last night to discuss the latest updates on the ash cloud.
A Downing Street spokesman said the committee agreed the Government should "continue to do whatever it can" to return stranded Britons to the UK.
Another meeting of the committee will take place today.
Ministers met yesterday following a clamour from airlines to restore flights, with carriers including British Airways pointing to the success of test flights to press home their arguments.
While travel organisations warned that it would be some time before travel and airports were back to normal, airlines were counting the cost of the disruption, which has seen a shutdown of UK airports since the end of last week.
BA said the flight ban had cost it around £15 million to £20 million a day.
Willie Walsh, BA chief executive, questioned the necessity of the hitherto "blanket ban" on flights, also said that European carriers had asked the EU and national governments for financial compensation.
The British Air Transport Association, with signatories and support from all major UK airlines, wrote to Transport Secretary Lord Adonis asking the Government "to commit to standing behind the industry financially at this very difficult time".
The International Air Transport Association was highly critical of the European response to the ash crisis which, it estimated, is costing the aviation industry around 200 million dollars (£130 million) a day.
Earlier, British Airways announced it would aim to resume some flights from London’s airports from 7pm today.
But in light of last night’s update from Nats, a BA spokesman said it was "reviewing" its schedule.
Manchester Airport last night said it was sticking with plans to open at 9am.
But a spokeswoman said it would monitor further updates from Nats.
British Airways announced it cancelled all short-haul flights today based on the latest information about the volcanic ash cloud.
The airline said it hoped to run long-haul flights scheduled to depart after 4pm, depending on a "full and permanent" opening of airspace.
It urged passengers to check flight details on ba.com before leaving for the airport.
A statement on BA’s website read: "Following the latest information from National Air Traffic Services about the path of the volcanic ash affecting UK airspace, we regret we will not be able to operate any short-haul flights on Tuesday 20 April.
"We were planning to operate short-haul flights scheduled to depart from 7pm, but these have now been cancelled.
"We are still hoping to operate long-haul flights which are scheduled to depart after 4pm on Tuesday 20 April, however this remains subject to the full and permanent opening of airspace."
BA said customers booked to travel on a cancelled flight would be able to claim a full refund or rebook their trip for a later date.
Newcastle International Airport confirmed it planned to reopen for flights to and from Aberdeen and the Isle of Man at 7am.
It also said easyJet was hoping to operate a "very limited service" from late afternoon.
Passengers were advised to check flight information before leaving for the airport.
A spokeswoman for Newcastle International Airport said the first flight was expected to arrive at 9.20am from Aberdeen.
However, Manchester Airport said, due to the latest advice from Nats, it was not planning to open before 1pm.
A spokesman said: "Unfortunately, the latest forecasts indicate that a further deterioration in conditions is likely.
"It is absolutely essential that people contact their airline before travelling to the airport because even if Manchester Airport is able to reopen today, schedules will take several days to return to normal."
EasyJet said all its flights to and from northern Europe including the UK were cancelled until 5pm, but it would continue to operate routes in southern Europe.
In a statement, the airline said it "had hoped to resume some services earlier, however, unfortunately based on the latest meteorological forecasts and continuing emission of volcanic ash into the atmosphere this is not possible".
The statement continued: "Passengers who are booked to travel on a cancelled flight should not travel to the airport but should instead arrange either a full refund or a free transfer to another flight on the same route within 30 days of the original flight date through easyJet.com."
The first flight out of Glasgow was scheduled to take off for Stornoway at 7am but did not make it into the air until 7.15am.
It was one of only a handful of domestic flights scheduled from Scotland this morning despite the re-opening of airspace.
At Glasgow, there was a trickle of passengers checking in at the airport for the first departure to Stornoway.
The departure board also listed flights to Islay, Campbeltown and Benbecula.
Some of the check-in desks were manned but there were no queues, and international departures for Tenerife and Amsterdam were listed as cancelled today.
Edinburgh airport had flights scheduled to leave for Stornoway and Belfast this morning, while a service to Newcastle was due to take-off from Aberdeen at 8.25am