Eruptions from the Grimsvotn volcano in Iceland persuaded Barcelona to travel to London for the Champions League final ahead of schedule, leaving Spain on Tuesday instead of Thursday in fear that the ash cloud could halt air travel later in the week. (Last year, Barca had to travel to its semifinal game against Inter Milan by bus because of an eruption at a different Icelandic volcano.)

The British Meteorological Office says there is "uncertainty" over how severe the problems may be while UEFA stated that, despite the potential problems, the game cannot be postponed and that it is powerless to help.

Around 25,000 Barca fans are expected to travel to London for the game. The club said it is still confident that all supporters will be able to fly, but if not they can take a 20-hour bus ride on Friday that leaves Spain at 9 a.m.

A Meteorological Office spokesperson said: "There is a lot of uncertainty through the week as the weather is changeable and the wind direction is variable. But [the] good news might be there is a not a persistent north-westerly like there was last year [when an ash cloud disrupted air travel throughout Europe]. It's very fluid and dynamic, so [the advice is] to keep a frequent check as the charts come out every six hours."