One year after an Icelandic volcano brought much of Europe's air traffic to a halt, a cloud of ash from a new eruption could spread to Britain by tomorrow, causing further disruption to airlines.

Iceland's Grimsvotn volcano, in its largest eruption for 100 years, began firing ash, smoke and steam 12 miles into the sky on Saturday.

The eruption has so far affected only Iceland, which, after initially playing down developments, closed its airspace. However, all airlines flying over Europe were told yesterday to prepare for a possible spread of ash to the continent later in the week.

The ash cloud could arrive in Scotland as early as midday tomorrow, said Europe's air traffic control organisation. The Met Office said it could spread to other parts of Britain, Spain and France later in the week.

The eruption is much stronger than the one at the Eyjafjallajokull volcano last April, which closed European skies for six days, amid fears that the ash could damage jet engines. But experts said the impact on air travel would be limited in comparison, due to favourable wind conditions and because the ash is heavier, and therefore likely to fall to earth quicker.

Richard Taylor, a spokesman for the Civil Aviation Authority, said the airline industry had "learnt lessons" from last year's eruption. "There will be changes to how we dealt with it that time around. You won't see the wholesale closures that were implemented back then, unless the ash concentration gets particularly dense."

His words were echoed by experts in Iceland. "It could lead to some disruption, but only for a limited time and only over a limited area," claimed the University of Iceland's professor of geophysics, Magnus Tumi Gudmundsson. "A very large area in southeast Iceland is in almost total darkness after a heavy fall of ash. But it is not spreading nearly as much. The winds are not as strong as they were last year."

The Icelandic air traffic control operator, Isavia, established a 120-nautical-mile no-fly-zone around the volcano, closed Keflavik Airport, the country's main hub, and cancelled all domestic flights. It said Keflavik would stay shut until at least noon today.

Transatlantic planes – including Air Force One, due to carry President Barack Obama to Ireland late yesterday – were told to steer clear of Iceland.

With winds currently blowing the ash northwards, authorities said there was little risk of any further disruption to European or transatlantic travel over the next 24 hours.