expensive legacy machines
You're not joking about expensive legacy machines. The trouble is we're stuck with having to pay a truly mind boggling amount for every legacy machine that is retained after DII rollout. So the RN and RAF introduce an aircraft management system for their Merlin fleets that's not supported (at the same time as DII rollout), and the system now requires NOA machines to function.
Cracking!
The shame is DII actually does seem to work!
(Vecvechookattack will know how much per legacy machine it costs, I'm sure)