Two Royal Navy ships have been deployed to help get stranded travellers back to the UK, Prime Minister Gordon Brown has said.
HMS Ark Royal and HMS Ocean will be made available for the relief effort, Mr Brown said, after a meeting of the emergency planning committee Cobra in Whitehall.
Mr Brown defended the continuing flight ban saying the safety of air passengers was "paramount" when dealing with crisis caused by the volcanic ash cloud.
Speaking in Number 10 Downing Street, Mr Brown said: "I think the first thing we have got to say is the safety of air passengers is of paramount importance.
"Today we are looking at the results of test flights that have been up in the air (on Sunday and Monday) and looking also at the manufacturers' recommendations, but that will be dealt with by the European Council meeting of Transport Ministers that will be held by video link later ... and further decisions about when flights can go and whether flights can not go will have to be made as a result of the conclusions of these meetings."
Mr Brown was flanked by Transport Secretary Lord Adonis and Foreign Secretary David Miliband as he spoke.
Mr Brown said: "We have large numbers of travellers who are trapped in Africa and Asia and the main route home at the moment is the airports that are open in Europe and that is in Spain.
"I talked to Prime Minister Zapatero and he has offered in principle use of Spanish airports as a hub to bring people back to Britain and we are now looking if we can make the arrangements necessary, the transport arrangements that we will support as a government, coach, ferry and train to get people either from Madrid or another Spanish airport back to Britain."
He did not elaborate on what role the Royal Navy ships would play but said further details would become available later today about the arrangements to bring people home.
Mr Brown said a third Royal Navy vessel, HMS Albion, on its way to Spain to pick up troops "may be able to be of help". He said: "I believe this is one of the most serious transport disruptions we have faced. It's got financial consequences as well as human consequences and we will do everything in our power to make sure all the arrangements are in place to help people where possible to get back home."
