Easter break disruption means those on school-sponsored trips and family holidays will not be back when new term starts

Many school desks will remain unoccupied tomorrow, despite the end of the Easter break, as continuing disruption to flights from the Icelandic volcanic ash cloud leaves thousands of Britons stranded abroad.

The continuing closure of British airspace means that large numbers of pupils and teachers will be unable to return from school-sponsored trips and family holidays abroad.

Restrictions on flights to and from the UK were yesterday extended until 1pm today on the advice of the National Air Traffic Control Service.

But major airlines went further, with British Airways cancelling all long-haul and short-haul flights in and out of the UK today and Ryanair grounding scheduled services to and from the UK and a range of European destinations until 1pm tomorrow. KLM has been carrying out test flights at lower altitudes, while Switzerland's aviation authorities began allowing flights.

With ferries and Eurostar services enjoying a surge in bookings, forecasters warned that there was still no sign a change in wind direction will clear the cloud, and vulcanologists said eruptions from Iceland's Eyjafjallajökull volcano could go on for months.

The cloud has prevented world leaders such as President Barack Obama attending today's funeral of Poland's late president, Lech Kaczynski.

Travel chaos warning, pages 6-7