If Yorkshire passengers can use Leeds Bradford Airport then, by the same logic, surely Southport passengers can use Liverpool Airport?
Of course the reality is that both of these airports only have a limited selection of flights, primarily to European package holiday destinations, whereas people for most other destinations will need to use Manchester Airport - which is the busiest airport in the country outside London.
That logic is reasonable for Southport, but West Lancashire, Wigan and Bolton are much less likely to use Liverpool Airport. I am aware that Manchester Airport has by far the most destinations outside London, however most people only go on 2 flights a year, one to a European package holiday destination and one back, but depending on where else you could be going, if you can find a flight to a European destination with a major hub airport e.g. Germany, then Liverpool or Leeds-Bradford airports may be useful.
I can tell you that about 2/3 of the flights I’ve been on have been from Manchester and the other third have been from Liverpool.
I would have said they should be allocated based on the demand that can realistically be served by rail - there will be certain flows where the route by rail is particularly circuitous and/or slow, whilst the route by road is quick and easy.
For example, based on those criteria, Stockport to Manchester Airport ought to have a very intensive train service. As it stands, there is one direct train each way per day, and despite discontent from Sheffield etc. passengers, that's the most it's ever likely to be again.
Several flows can be strung together from the list of towns and cities that has been compiled in order of priority based on distance and population, often serving others which wouldn’t justify a service of their own along the line, e.g. Southport-Burscough-Wigan-Westhoughton-Bolton-Castlefield-Airport.
Yes, Stockport ought to have an extremely intensive direct rail service to the nearby airport (not reversing at Piccadilly) but unfortunately the track layout precludes since the airport is on the Stockport avoiding line. There are 2 competing options to resolve this, either allow this short distance Stockport - Airport traffic to be carried by the roads, or build new rail infrastructure to connect Stockport to the airport directly. I suspect the compromise will be the latter in the form of one of the next extensions of the Metrolink. Unfortunately neither of these help Sheffield, who are in a very bad position now but not because of Southport since the Sheffield service (from the east) never ran via Castlefield.
Southport is a town with a population of 90,000. Even if the entire population of West Lancashire lived near to a Southport line station, that would only be another 110,000 people. Wigan is the first place en-route that is of any notable size, having 107,000 people (330,000 within the entire borough). Bolton has 139,000 people (262,000 within the entire borough). So in total you are talking about, at most, 792,000 people.
As close as they may be, the West Yorkshire Urban Area has a total of 1.8m people, let alone York and beyond - or any of the other places from which people might feasibly railhead into an Airport service.
In terms of distance, Southport to Manchester Airport is 36 miles as the crow flies, whilst Huddersfield to Manchester Airport is 28 miles and Leeds is 43 miles away.
These look to be reasonable estimates of population, so by my own system the Southport - Airport service has a priority of 22 and the Leeds - Airport service has a priority of 41.86, so a service from Yorkshire proves to be almost twice as important to have, which isn’t surprising given the size of Leeds as one of the largest cities in Great Britain. I would have used the distance to the centre of Manchester itself and run the highest priority Castlefield services through to the airport, but it still provides a good illustration.
It's also worth noting that Wigan and Bolton will have their own services to the Castlefield corridor (even if not the Airport), so really this is about the stations between Wigan and Southport.
If we look at what other services there are, there is a Southport - Stalybridge, Clitheroe - Rochdale, Kirkby - Blackburn, Wigan - Leeds and Preston - Victoria all running to Victoria, with Castlefield services provided by Southport - Alderley Edge, Blackpool North - Hazel Grove/Airport and Barrow/Windermere - Airport, with only an hourly service from each of Wigan and Bolton running through to the airport. If the Barrow/Windermere services were diverted via Bolton, Wigan would have then lost all airport services, which is concerning for a part of Greater Manchester.
In an ideal world, everyone would have through services to the Airport. But that's not the world we live in, and so compromises are needed.
I think the optimal solution involves a clockface 2tph Manchester Airport - Bolton with one extended to Blackpool North and the other extended to Southport, with the other Southport running somewhere via Victoria and the other Blackpool running to Hazel Grove as it has done for many years.
In my view, priority ought to be given to those services which currently run (as is the case under the Network Code) and which have existed for the longest time - bearing in mind that some people will have moved to places based on the train service in place. Remaining capacity should be allocated based on demand.
So if you were to make this assessment in early 2018, you would have given priority to the Southport - Airport service that was currently running and had been running since 1998? Most of the demand from stations between Wigan and Southport is to the south side of Manchester and Piccadilly and this has been scientifically assessed to be the case many times.
Southport isn't to blame for the infrastructure limitations, no, but given these limitations, there is always going to be winners and losers.
And given that background, IMO it is unreasonable to subject CLC "fast" passengers to lots of additional stops (as will be the case under the new timetable) whilst still disadvantaging users of certain stations through the loss of the half-hourly, cross-Warrington stopping services. All because Southport line residents created a sufficient political nuisance to stop the original proposals from coming into place.
The issue with the CLC line east of Birchwood is that there are too many non-stations opened at various points in time which are now too close together and on an unelectrified line it is unreasonable to require longer distance passengers to endure stops at all of them. I would concentrate service on Irlam and perhaps one or two more, but close the rest. West of Warrington, all stops with only Hunts Cross, Halewood, Hough Green and Widnes above the “fast” service pattern is not unreasonable.
The main service requirements for how the CLC line is used are for Warrington West to Padgate, Birchwood, Castlefield and the Airport, Birchwood and Padgate to Warrington West, Liverpool South Parkway and Lime Street and all of the above to Warrington Central. It is even more unreasonable to terminate services at Warrington Central. If they must not be through services, then services from Liverpool should terminate at Birchwood and services from Manchester should terminate at Warrington West, giving a doubled frequency across Warrington.
It has been proved at Ormskirk and Kirkby that non-through services are unworkable and no more should be split like this. Ultimately it is likely that the Merseyrail service will be extended from Liverpool Central and Hunts Cross to Warrington Central or preferably Birchwood, but with the requirement for continued through services from Lime Street to Manchester with a reduced number of stations east of Warrington.
The other thing that is unreasonable is requiring the Southport - Stalybridge service to serve the stations between Bolton and Salford Crescent given the distance it has travelled. The stations between Victoria and Rochdale are served by a service terminating there. It would be equally unreasonable for the Clitheroe service to serve them instead for the same reason, but it would have the justification of stations north of Bolton and east of Victoria. The best service for them would be the electric Preston - Victoria or failing that one of the Blackpools run by a fast accelerating 331 and not a 150.
There's not going to be a Southport to Manchester Piccadilly or Manchester Airport service regardless of what happens next, so I am unsure what the point you're making is.
There’s not going to be a Southport - Piccadilly/Airport service in the MRTF B+/December 2022 timetable, but it’s unlikely that there will never be one again, especially after the infrastructure constraints are resolved. The service pattern is likely to be reconfigured several times over the next 10-15 years pending the outcomes of infrastructure work in the area.