Disruption to air traffic is relatively rare in the zone overseen by the London Volcanic Ash Advisory Centre, one of nine monitoring sectors which track ash plumes in order to assess potential risks to airspace.
Ash from a volcano in the region of the Eyjafjallajokull glacier in Iceland has resulted in closure of airspace in Scandinavia, the UK and Ireland and the cancellation of thousands of flights.
Last month the International Airways Volcano Watch Operations Group summarised notable activity from the nine ash-monitoring centres, over the previous 18 months, during a meeting in Lima.
VAAC London experienced no volcanic activity in its area of responsibility, the group stated. The London monitoring zone includes Iceland, the origin of the plume disrupting air traffic in Europe today.
In contrast VAAC Buenos Aires issued 492 ash advisories, for four volcanoes, in the period between July 2008 and October 2009, while the centre in Tokyo transmitted 76 with respect to Russia's Sarychev Peak in mid-2009.
Wellington centre - which has extended its area of responsibility to account for increased Antarctic air operations, and more long-haul traffic from Australia and New Zealand to South America - issued 44 advisories over volcanoes in Tonga and Vanuatu.
Three simultaneous eruptions during August 2008, described by the operations group as "unprecedented", resulted in a "challenging" workload at the Anchorage centre, while air operations experienced "significant impact" from the eruption at Mount Redoubt in March-April last year. The operations group says the Redoubt eruption "may have proved to be the most costly" in Alaska's history.
Washington centre had a "busy reporting period", it adds, with advisories for Ecuador and Montserrat, but activity at Toulouse was "very weak" with fewer than 10 transmitted between July 2008 and November 2009.
Two other VAACs are located in Montreal and Darwin.