EastofKoksy - our airline friends DO make their fuel calculations to maintain 6000ft til DET/DVR before being cleared higher. This is a major driver behind the LAMP project as the most inefficient phase of flight through the London airspace at the moment is the initial departure phase. The eventual idea is for aircraft to depart LL/KK/SS/GW climbing to something in the region of 10000ft on the SID, making huge cost saving (fuel) benefits. The stacks will be reduced to two for Heathrow and will be higher and farther out giving further benefits to incoming traffic too.