An interesting use of public funds to the benefit of a private [airport] company in which one would have thought, the EU's Competition Commission might take an interest..
So too, the M25 signs which, with the exception of the ones on the approach to Junction 21, only direct drivers to Stansted and Heathrow (and Gatwick). Even the new ones erected near Heathrow following the road widening only refer to Stansted.
(BTW, London City doesn't fair any better!).
Obviously, the neddies in the Dept of Transport (Road Signs Section) haven't heard of Luton (or London City) or they failed geography GCSE and believe Luton is located in the Midlands and London City on the Essex coast!!