AIR cargo is still under threat of disruption from Icelandic volcanic ash cloud, but so far it has not caused major congestion for anything but short periods this week.

Eurocontrol expected 28,500 flights took place in Europe on Monday, which is 500 below the average for a Monday this time of year, reported London's International Freighting Weekly (IFW). Airports were closed briefly in France, Italy, Spain, Portugal and Luxembourg at various times, but soon reopened.

Cargolux, Europe's biggest cargo airline, suffered a shutdown of its main Luxembourg hub, but it too re-opened. "We have had delays, but nothing too significant," said company vice president Robert van de Weg.

"We had to bring some of the aircraft in this morning, as opposed to last night, and some of our transatlantic flights were delayed because they had to fly longer routes [around the ash cloud], but so far it has had a marginal impact," he said.

"The big question, though, is what will happen for the rest of the week. We are watching the situation very closely, because there is a big, dark cloud over the Atlantic, and if the wind comes in from the west, we could be in for some more challenges," he said.

Eurocontrol said: "There is an area of ash cloud in the middle of the north Atlantic, which is impacting transatlantic flights. Many have to make significant re-routings to avoid the ash cloud, resulting in delays.

"According to the forecasts, during the afternoon, areas of higher ash concentration could move in a north-easterly direction over the Iberian peninsula," said the statement.

Said Mr Van de Weg: "Demand is very strong, but it was strong before the European airspace closures, so it is hard to know now whether the high demand now is still related to the closures."

The UK's Business Financial Wire reported that despite the volcanic disruption, cargo tonnage in April was up 6.2 per cent on last year and this reflects the underlying strength of the air cargo business.

The report also quoted the British Airports Authority (BAA) saying passenger traffic slumped 22.7 per cent last month as a direct result of the ash.

Worst hit were Southampton and Edinburgh airports, where passenger numbers tumbled 27 per cent and 26 per cent respectively. Heathrow and Stansted were both down 21 per cent, said the report.