On 5 September 1999 Dirk-Jan Swier and Michiel Panhuysen opened the artificial climbing route 'Quod Erat Demonstrandum' (A3) on the control tower of Schiphol airport (Amsterdam, The Netherlands).

The route is approximately 60m high, but it starts more than 12 meters BELOW sea level. You have to climb along a hold-less concrete wall.

For the ascent they used dyneema slings and carabiners attached to the lightning conductor. A battery powered drill was used to install 15 "M10" bolts during the ascent. 5 "M6" bolts were drilled at the top of the route to attach the banner with the slogan.

Three hours were necessary for the ascent. Two hours were used to unfold the banner. The banner measured 4*30 meters. To fasten the bottom part they had to rappel down and then they ascended again using jumars. In between they rested using a mini-portaledge.

The platform from which they started their climb and the tower are forbidden terrain for non-employees. It is protected by a security firm and by the military police, who arrested the two climbers at the end of their climb. They could not understand how they were able to ascend an obviously "unclimbable" tower.

The Military Police (Koninklijke Marechaussee) did not try to halt or disrupt the action after Milieudefensie assured them that the air traffic would not be disturbed by the action.

• The climber's comments

• We arrived very early in the morning. No one was expecting us.
• We carefully sorted our gear-bag in "last in - first out" order. The M6 bolts, the portaledge and the film were at the bottom.
• We were afraid to drop something. Therefore the ground-crew were all wearing helmets. In the end we only dropped one smaal rope-loop and two protective glasses.
• We hoped the lightning-conductor would hold us. We used etriers to ascend. Now and then we placed a bolt for better protection.
• We almost got sick from the exhaust fumes from all the airplanes. a gas-mask would have been useful.
• After ascending 10m we knew we were relatively safe. The police would need special equipment to get us down. That gave us at least one half hour to continue.

Reports and pictures of their action appeared on Dutch TV (NOS Journaal) and in several newspapers (Trouw, Volkskrant, Spits, Metro.)

The Dutch government decides about a new environmental contract for Schiphol Airport that will run until 2003. Milieudefensie wants to remind the ministers that they promised to reduce the noise level and the emissions of the airport. But if the air traffic exceeds 460.000 flights per year the ministers cannot keep this promise.