The ash from Icelandic volcano Grimsvotn could affect at least some flights in Europe, according to several sources.
Although the most recent eruption isn't likely to cause anything like the disruption seen in the wake of the Eyjafjallajokull ash, which led to a huge shutdown of European airspace in April last year, several agencies have warned that some areas of Northern Europe could see closures.
According to the latest predictions from the UK's Met Office forecasters, ash could be present at low altitudes in Northern Britain and parts of Russia from around 6 AM UTC May 24.
That means that there is a possibility of flight operations in Ireland and Scotland being affected, although European air traffic body Eurocontrol says that unstable meteorological conditions make it harder to predict any further.
The UK's Civil Aviation Authority (CAA) says that there "is the possibility of ash reaching Scottish airspace from Tuesday onwards, and affecting other parts of the UK and Ireland later in the week," adding that it can't rule out disruption.
In any case, following last year's eruption, airlines now have agreed procedures in place which allow them to fly through through medium-density ash clouds and meaning only significant quantities would cause flight problems.
Keflavik Airport in Iceland, which was closed over the weekend when Grimsvotn started to erupt, has now reopened, although flight disruption is continuing.
Travelers should check with their airline before departing.
Other useful sources:
UK Met Office, London Volcanic Ash Advisory Centre:
Airport Flight Status: http://www.flightstats.com
EuroControl on Twitter @Eurocontrol
Twitter hashtags: #ashcloud, #grimsvotn and #ashtagReuse content