To be honest I am not sure. I have heard a range of things from not enough tower controllers to run the two runways simultaneously one for departures and one for arrivals as was planned, to landing aids and SIDS/STARS not being approved for new runway. I am not sure of the real reason but right now it is making no difference to the congestion problem we have in Dubai as either one runway or the other is used at any one time but not both. If only we could go back to 2 years ago when we were able to provide 10 NM spacing through all gates, the delays we have now would not be happening.