One of the largest travel agencies in New Zealand on Friday said it may take days before normal flights resume due to volcanic ash over Europe, local media reported. Flights in many countries are canceled following the eruption of a volcano in Iceland which sent a huge plume of volcanic ash into the air which can damage plane engines. The entire airspace in Britain, Ireland, Norway, Denmark, Belgium and Sweden is closed on Friday. There are partial closures in France, Germany and the Netherlands. Finland has closed all airports except Helsinki-Vantaa. New Zealand's House of Travel said about 4,500 clients were affected. The agency is identifying all those due to travel in the next few days and contacting them to discuss their options, Radio New Zealand reported on Friday. House of Travel spokesman Brent Thomas said no one knew how far the volcanic ash was going to spread. Air New Zealand flights from London to Auckland via Los Angeles and Hong Kong, which were scheduled to arrive early on Saturday ( NZT), have been canceled. The airline said there was a high probability that two London- bound departures on Friday night would terminate at Hong Kong and Los Angeles. Passengers are advised to defer their travel plans. 