US President Barack Obama is flying from Ireland to the UK ahead of schedule because of the possible disruption to air travel caused by the Icelandic ash cloud, the White House said.

The President had been due to arrive on Tuesday for his state visit.

But the decision was taken to bring forward the visit as the first commercial UK flight cancellations were announced.

With ash forecast to reach Scotland by the evening, Glasgow-based carrier Loganair said it had axed 36 flights on Tuesday.

White House deputy press secretary Josh Earnest said: "Due to a recent change in the trajectory in the plume of volcanic ash, Air Force One will depart Ireland for London tonight. The schedule for tomorrow will proceed as planned."

Transport Secretary Philip Hammond said the ash, from the eruption of Grimsvotn in Iceland, has already caused "modest delays" to some flights, including some Atlantic services.

He also warned that there could be further disruption later in the week.

But Mr Hammond and the Civil Aviation Authority (CAA) stressed that the UK is in a much better position to deal with the latest problem than it was last year when the eruption of Iceland's Eyjafjallajokull caused the closure of airspace and the cancellation of thousands of flights.

Loganair said it had cancelled all its flights due to depart between 6am and 1pm on Tuesday, except its inter-isles flights in Orkney.