chesna152 Makes valid point which I also raised a week or so ago. Luton is now sitting at 12.5 million passengers and probably between 13.5 and 14 million passengers this time next year. I doubt that it would need a dedicated rail link to hit 18 million passengers but if it did those extra 4 million passengers would not all use a train so the cost for that final push would be huge for a small return.
My thinking is that 18 million passengers is not the end game but the start of a push beyond 18 million passengers with ultimately expansion to the south of the runway and a terminal 2. There would be no other reason to spend that sort of money for so little return but then that side of the airport would also need the link.
Finally I would be quite happy to see a few services head for Southend from Luton as Luton would not even miss them now while it would make a big difference to the fortunes of that airport.