The Dutch Onderzoeksraad (Dutch Safety Board DSB) is investigating in a so called "short term study" how it was possible that tower cleared a number of flights for takeoff from closed runway 18L, also known as Aalsmeerbaan, between about 20:20L and about 20:40L.
The Dutch Safety Board reported on Jun 21st 2012 that the runway had been closed at 17:30L (15:30Z) and was under control by the Airport Authority with the possibility of trucks crossing the runway. The runway had not yet been released by the Airport Authority to Air Traffic Control when tower cleared flights for takeoff from the runway for a period of about 20 minutes starting at about 20:20L (18:20Z). The closure of the runway was not indicated in the NOTAMs.
Netherland's Luchtverkeersleiding (LVNL), the ATC service provider in the Netherlands, reported all 9 flights departed without incident in clear weather and on a clearly visible runway. The tower controller had full view of the runway and could have intervened in case of obstacles on or approaching the runway, however, no other traffic or obstacles were on or near the runway during those 20 minutes. The LVNL said that other airport work related traffic could have entered the runway without clearance as the runway was closed for air traffic. The error was detected when the airport authority actually returned the runway to ATC, all relevant authorities including the DSB were immediately informed. In addition the LVNL have opened an internal investigation.
Radar data show the last departure from runway 18L before closure was at 15:29Z, the next departures were (list most probably incomplete): at 18:11Z (C25B), 18:29Z (B737, KL-1369), 18:37Z (F70, KL-1512), 18:39Z (B737, KL-1659), 18:41Z (A318, AF-1357), 18:44Z (A319, AZ-117), 18:45Z (B738, KL-1681) and 18:49Z (B738, AT-853).