Thanks for the info, all.
BDiONU
3) Is the proprotion of Mode A codes in use published somewhere?
4) You seem to be suggesting that the upgrades to ground equipment to take advantage of Mode S will be delayed against an original plan. Are there details published of a) the original plan and b) the revised schedule, or are you deducing the inevitability of delay from NATS's dire financial situation?
Mike
5) What is the FAA policy on aircraft equipage with Mode S? Is it required on aircraft over a certain size, or Part 121/135 or something else? What's the plan for the future?
6) What are the consequences of the code shortage? Does it delay flights? Do you limit capacity to cope with the extra workload of having to use these local codes? What's the "cost" of the problem?
BTW I can answer part of my question 1 from published Eurocontrol Mode S stuff. When Mode S is fully implemented, a conspicuity (non-unique) Mode A code will be allocated to aircraft. But I would appreciate any guidance as to how far down the road to Mode S we have to go before discrete Mode A codes start being preserved by that process.