THE HAGUE - KLM Royal Dutch Airlines conducted a test flight from Amsterdam to Dusseldorf on Sunday, it said, with eight more to follow during the day to measure the impact of volcanic ash on aircraft.

'A Boeing 737 with 20 crew on board departed from Schiphol airport at 0430 GMT (12.30pm Sunday Singapore time) and landed safely in Dusseldorf in Germany,' KLM spokeswoman Joyce Veekman told AFP.

KLM ran a similar test flight on Saturday evening within Dutch airspace, flying up to 41,000 feet (about 13,000 metres), with KLM chief executive Peter Hartman saying afterwards that 'we observed no irregularities'.