Both Derby and the Airport would have long rural sections that aren't ideal for trams, and with the relatively slow access to Nottingham wouldn't be time-competitive for end to end journeys against trains or express coaches. I know there isn't an express coach or a train to the airport, but the fact there isn't itself says something about the size of the market.
RE: a coach - there used to be a bus running pretty direct, but prior to the A453 widening (which was only fully opened a few weeks ago) it kept getting stuck in the heavy traffic and therefore was rather unappealing. It's unsurprising that a RailLink bus has been reinstated between the Parkway and Airport within a matter of weeks of the A453 works being (broadly) finished.
With regards to the distance, at the moment that is certainly true, however in the medium term plan there are a couple of major developments in the pipeline which, if they happen, would change both the demand (from new residents and employees) and the distances involved.
The first development is essentially a new housing estate the size of Clifton right next door to Clifton (heading south west alongside the A453 corridor) taking you all the way down to Barton Lane which used to join the A453 at Barton-in-Fabis.
http://www.rushcliffe.gov.uk/media/.../Amendments to Policies Map_final_low res.pdf (Page 10 Printed, 11 Digital)
The second development is a proposed huge industrial estate/rail freight terminal planned north of East Midlands Airport (basically filling the land between Castle Donnington and the Airport / M1 South and East of Lockington.
http://www.eastmidlandsgateway.co.uk/masterplan.php ).
There is also the planned HS2 station at Toton Sidings.
Depending on the exact route chosen you would then have an extension which runs:-
Clifton, multiple stops through "Clifton 2", Gotham, East Midlands Parkway, Kegworth, East Midlands Cargo, East Midlands Airport, Donington Park, Castle Donington, East Midlands Gateway.
Or potentially a pair of extensions :-
1. Clifton, multiple stops through "Clifton 2", Gotham, East Midlands Parkway, Kegworth, East Midlands Cargo, East Midlands Airport
2. Toton Lane, Toton HS2, Long Eaton, Sawley, East Midlands Gateway, Castle Donington, Donington Park, East Midlands Airport.
If you choose the Clifton only version:-
With the lengthy rural running the journey times here have the chance of being pretty quick, and if it's built during the construction of "Clifton 2" / "East Midlands Gateway" it stands a chance of attracting a fair number of employees at the new rail freight terminal to the new estate, provides a direct link to the airport for a significant part of the Nottingham population.
If you choose the pair, you've now connected the Airport near-directly to HS2 making it more attractive for journey's beyond the East Midlands, you've connected the QMC and University (particularly useful for there own international exchanges and visitors).
If you then consider tram trains would it be too wild to suggest a couple a link with the MML at Kegworth - therefore allowing tram-trains (or potentially "real trains" if you build the route through the airport segregated) to run from Derby and Loughbourgh (or further afield) direct to the airport, heck even Lincoln - Newark - Nottingham - Beeston - East Midlands Parkway - East Midlands Airport...
I did the two new lines on Thursday. I was quite surprised as to how much of the former Great Central Main Line has been incorporated into the clifton South branch as I was always led to believe that most of the formation between Nottingham & Ruddington hqd been re-developed.
The route through the Meadows has completely vanished - the only evidence I've found is a short gap in the "steps" on the embankment alongside the River Trent where the old bridge supports used to be.
South of the river it's a lot easier to follow the line - prior to the construction of Line 2 the embankment existed from the River to Cornonation Avenue (some of this was demolished to allow extra flood alleviation measures), it then continued all the way to Wilford Lane, then resumed south of Wilford Lane where you could join an unpaved footpath alongside it all the way to Ruddington Lane (by which time it was in a cutting). You've then got a nature reserve where the line does it's 90 degree turn under the A52, and south of there it's open fields - and the only non-tram development of any note south of the Trent - some new housing on Old Station Drive in Ruddington.
