Thousands more delayed as ash drifts south

Passengers from destinations as far apart as the Canaries and the Caribbean were last night struggling home after ash from the Icelandic volcano of Eyjafjoll once again disrupted flights. Dozens of departures were cancelled and thousands of passengers encountered severe delays, amid fears that continued disruption could seriously weaken UK airlines.

Nineteen Spanish airports closed on Saturday because of high concentrations of ash; by yesterday, southern Germany, Switzerland, northern Italy, southern France and northern Portugal were affected. Europe's biggest airline, Ryanair, cancelled dozens of flights across the western half of the continent. British Airways and easyJet grounded departures to and from Italy, France and Spain.

Monarch was one of the few airlines to operate all its flights – but the carrier also suffered some serious delays. A scheduled overnight flight from Sanford in Florida to Gatwick due to arrive at 5.30am on Sunday was delayed by 18 hours. Passengers on a Thomson flight from Sharm el-Sheikh to Gatwick who were due in at 2am on Sunday morning were expected at 8pm.

While the skies over the Canaries were clear, the ash exposed a particular problem for travellers to this Atlantic archipelago. Many of the aircraft that routinely shuttle to and from the UK operate close to the limits of their range. Diversions extend flight times, requiring refuelling stops – a procedure made more complicated when airports in Spain and Portugal are closed.

Heathrow's longest delay was on British Airways from the Bahamas, running 12 hours late. Manchester-bound passengers on Thomson from Cancun in Mexico and on Thomas Cook from Montego Bay in Jamaica faced delays of six hours.

A tongue of volcanic dust drifted south over the weekend into the Atlantic then curled around to sweep over Europe from northern Portugal to the Alps and beyond. Transatlantic departures faced long diversions, an expensive business for airlines: if flight times are extended by a couple of hours, passengers with connections miss their flights and have to be rebooked and looked after at the airline's expense. In addition, an extra pilot may need to be drafted in. With most carriers working at full stretch, delays can snowball rapidly. Many passengers for the Caribbean, Canada and US faced long waits because their aircraft were late arriving at the UK gateway. Problems were compounded at Heathrow because of the extreme pressure on slots. Virgin Atlantic flights to and from the east coast of the US were particularly badly affected.

Andrew Haines, the chief executive of the Civil Aviation Authority, and the man responsible for UK air safety, warned "Ash is likely to continue to disrupt UK air travel for the foreseeable future".

Disruption set to continue

By Steve Connor, Science Editor

*An anticyclone in the North Atlantic is likely to increase the risk of Icelandic volcanic ash blowing into British airspace – and at the same time blow cool northerly winds over Britain in the next few days. Known as a blocking high-pressure system, the anticyclone is preventing the usual south westerly winds from blowing in milder, moist air from the Atlantic.

As temperatures in London yesterday struggled to get into double figures, Moscow bathed in 25C heat. It follows a similar weather pattern to the previous few months which allowed cold, dry winds to blow over Britain from the north-east, bringing one the coldest winters in living memory.

Some scientists predict that the pattern is likely to continue into summer because of the influence of solar activity on the jet stream, the high altitude winds that usually blow from the south-west over Britain, dominating its weather. The researchers found a link between low solar activity – few sunspots – and alterations in the jet stream that result in northerly winds over the UK.