Norfolk travellers stranded abroad because volcanic ash has grounded their flights home look set for more misery after UK flights were grounded at least 1am tomorrow (Tuesday).

Norfolk travellers stranded abroad because volcanic ash has grounded their flights home look set for more misery after UK flights were grounded at least 1am tomorrow (Tuesday).

The ash cloud has prevented nearly all flights, including all in Norwich, from entering or leaving the UK since noon on Thursday, wrecking travel plans and leaving thousands stranded.

The flights are grounded because of concerns the ash from the Eyjafjallajokull volcano would be sucked into engines and cause turbines to grind to a halt.

Air traffic control company Nats said conditions around the movement of the layers of the volcanic ash cloud over the UK “remained dynamic”.

Nats said it was maintaining close dialogue with the Met Office and with the Civil Aviation Authority and that its next flight update would be made around 3pm today.

But some airlines, questioning the science behind the no-fly rule, yesterday carried out safety tests, flying empty planes at relatively low altitude to discover what effect the ash would have.

Dutch carrier KLM, which operates some flights to and from Norwich International Airport, flew several empty planes from Dusseldorf in western Germany to Amsterdam's Schiphol Airport at an unspecified altitude above 10,000ft.

They did not encounter the thick cloud of ash, whose main band floats between 20,000 to 32,000 feet, the height of most commercial flight paths.

The Foreign Office website (www.fco.gov.uk) contains advice for stranded UK citizens. UK citizens needing consular assistance can contact the embassy in the country they are in; contact details are available on the Foreign Office website.

An emergency number - 020 7008 0000 - is available for relatives of stranded UK citizens who are concerned about the safety or well-being of their loved ones.

Prime Minister Gordon Brown apologised to travellers, saying he was sorry there had been so much inconvenience.

The government indicated last night that the Royal Navy could be used to ferry passengers back to Britain.

Travellers have been trying to find alternative modes of transport, with Eurostar services full and ferries packed.

Liberal Democrat leader Nick Clegg had been due to fly to Norwich today, but that has been cancelled.

There is also some concern that the homecoming of the Royal Anglians could be delayed. The soldiers are due to fly back to Pirbright in Surrey tomorrow, but the majority of military flights have been suspended.