Theoretically you might be able to get 20 or more aircraft holding over one point - they are separated by 1000 ft vertically. However, the amount of space available in the vertical plane may be limited by traffic overflying or other constraints. Similarly, the horizontal dimension of the holding area is clearly defined so that aircraft holding do not conflict with aircraft passing close by, or holding in adjacent holding areas (but this does not necessarily limit the number which can be held). During very busy periods, perhaps during low visibility operations, the "inner" holdings stacks (of which Bovingdon is one) will take a certain number of aircraft (my aged brain won't remember the limit) and subsequent aircraft are held further out at much higher levels..
It's all clever stuff!
All the best...
Last edited by HEATHROW DIRECTOR; 14th November 2005 at 13:02.