Britain's two busiest airports have closed as a volcanic ash cloud drifts further south, threatening major disruption to many thousands of people. A no-fly zone imposed by the Civil Aviation Authority sees Heathrow, Gatwick and London City airports shut from 0100 BST until at least 0700 BST. Flights are also grounded in parts of Scotland and Northern Ireland. Manchester, Liverpool and Leeds Bradford airports have re-opened after restrictions in the north were lifted. Birmingham, Norwich and East Midlands airports are also open again, after suspending flights on Sunday. Prestwick Airport will also no longer be within the no-fly zone from 0100 BST, although a spokeswoman said it would not be receiving any flights for another 12 hours. According to air traffic authority Nats, other airports closing through the night include Farnborough, Shoreham, Biggin Hill, all airfields in Northern Ireland, Scottish Western Isles, Oban, Campbeltown, Caernarfon and Aberdeen. It said Cardiff would remain open but operations may be limited due to its proximity to the no-fly zone. Flights in and out of Dublin, in the Irish Republic, are also grounded until at least noon. The Department of Transport has warned restrictions are likely across different parts of the UK until at least Tuesday. Travellers are being advised to check with their airline before leaving home. The latest dense patch of ash has already disrupted the travel plans of tens of thousands of people, mainly in northern parts of the UK. Airspace over Northern Ireland was first to close on Saturday, then as the cloud moved south, Manchester closed at lunchtime on Sunday, with Birmingham following suit by teatime. Virgin Atlantic president Sir Richard Branson called the closure of Manchester airport "beyond a joke". "All the test flights by airlines, aircraft and engine manufacturers have shown no evidence that airlines could not continue to fly completely safety," he said. British Airways said airlines should be able to decide whether it was safe to fly, as the current approach was "overly restrictive". But the CAA chief executive Andrew Haines said: "We are all working flat out to keep flying safe whilst minimising disruption from the volcano." Ash from the Eyjafjallajokull volcano has led to thousands of flights being delayed or cancelled since April. Source: BBC