Several test flights were staged by airline companies such as Air France and Germany's Lufthansa on Saturday to assess the air traffic conditions in the wake of Wednesday's volcanic eruption. Almost all those flights landed without major damage caused. But people are still cautious.

Successful test flights would not mean that passenger flights will resume soon, head of the Royal Dutch Airlines KLM Peter Hartman said, adding the KLM will conduct more test flights to study the impact of volcanic ash clouds on aircraft.

The volcano in southern Iceland's Eyjafjallajokull glacier sends ash into the air Friday, April 16, 2010. [Xinhua]

A Urals Airlines passenger flight from Moscow to Rome that landed at the Vienna International Airport on Saturday was checked and no apparent damage was found to the engines of the Airbus A321 plane.

The unintended "manned flight" did not show signs of damage by the volcanic ash which consists of harmful materials which could cause plane engines to stop working mid-air.

The KLM has decided to operate nine more test flights on Sunday, after the first, from Duesseldorf to Amsterdam, landed safely with no damage to the Boeing 737-800 aircraft late on Saturday.

In a statement, the KLM said if all of the test flights were operated without a hitch, the KLM hopes it would receive permission to resume part of its normal operations as quickly as possible to bring passengers to their destinations.

Air France also said on Sunday that it would plan some long-distance flights on Monday, weather permitting.

The volcano in Iceland keeps spewing ash into the atmosphere and the ash cloud covers an area stretching from England to Belarus and has reached heights of up to eight km.