Britain was today suffering major disruption again after the return of the Icelandic ash cloud.

A no-fly order saw Heathrow and Gatwick shut until 7am today, and both will only partially reopen during the next six hours, air traffic authority Nats said.

Flights are also grounded until lunchtime across Northern Ireland and much of Scotland and Wales, with warnings of widespread knock-on disruption later in the day both here and abroad.

The chaos has also had a knock on affect on Southampton and Bournemouth airports with a string of cancellations and delays.

There will be no arrivals at Gatwick until 1pm at the earliest, while Heathrow will see reduced take-offs and departures as well as extended delays and cancellations.

Some big regional airports like Manchester, Glasgow and Stansted are open, but passengers everywhere are being urged to check with their airlines before leaving for the airport.

Nats warned the ash cloud was ''continuing to change shape'' as it spread over southern England to Northern Ireland and as far north as the Shetland Isles.

The latest air travel chaos comes a month after the Eyjafjallajokull volcano eruption cancelled a swathe of flights across Europe, and as talks continue to avert a crippling five-day strike by British Airways cabin crew.

There are warnings that the ash restrictions could persist in the UK until tomorrow.

Forecasters are expecting a change in the north-westerly wind direction today, which is expected to blow the ''high density'' cloud from the Eyjafjallajokull volcano away from Britain on Tuesday.

Earlier revisions to the no-fly zone meant airports in the north of England like Manchester, East Midlands and Leeds Bradford reopened from 1am today, after being closed for most of yesterday.