A Scottish Air Force has to be looked at in the wider context of an independent Scotland. One of the main arguments for Scottish independence is the belief that Scotland contributes more financially to the UK than it gets back (aka "The English are stealing our money"). The last lot of figures I saw (I think it was 2012) had Scotland raising over £1bn more in taxes for the UK exchequer than the UK Government granted back to the Scottish Government for spending in Scotland. This however doesn't take into account the services and spending that Scotland has access to at a UK level - the biggest example being defence spending, but there's also other stuff like the diplomatic service, border control, issuing of passports and visas, vehicle registration and driver licensing, air traffic control, intelligence and security services and the umpteen other things that are paid for at a UK level.
One of the other main arguments for independence is that by various socio-economic measures - e.g. child poverty, drug and alcohol abuse, heart disease rates - Scotland is the worst place in western Europe. The argument is an independent Scotland can better tackle these problems. Scotland already has the highest level of public spending per capita of any region in the UK. Alex Salmond has made some grand promises with regards to public pensions, welfare, education and public healthcare. Public spending in an independent Scotland is already going to be sky high before we even consider defence, which let's be fair is pretty far down the list of priorities for most Scottish voters.
Some people have advocated a basic asset split based on Scotland's percentage of the UK population (around 8%). They think that the starting position for negotiations should be Scotland gets 8% of everything - including defence hardware. That's obviously very impractical and unworkable. GDB correctly points out the Yes Campaign published its independence white paper in which it stated the core of an independent Scottish military would be made up of one squadron of Typhoons, a number of C-130J, a number of utility helicopters, 3-4 frigates, a number of offshore patrol vessels and a mechanised infantry brigade.
I've already outlined why the financial situation in an independent Scotland is going to be pretty tight even before Alex Salmond has had to pay for all the public spending promises he's made. Exactly how Scotland will be able to fund such a military as was outlined in the independence white paper is open to some very serious question.
Perhaps the most telling thing about the Yes Campaign's defence plans is how they have totally failed to even address the personnel question. As moo points out - are there enough Scottish pilots in the RAF to form a Scottish AF
? Are there enough avionics maintainers? Are there enough marine engineers in the RN
to form a Scottish Navy? Enough naval warfare officers? Enough infantry officers?
Are there enough Scottish personnel in the UK Armed Forces across the huge range of jobs, roles and skills required to form an independent Scottish military? More pressingly, are enough of them prepared to transfer to an independent Scottish military? I know a guy who is a cavalry officer in the British Army and he says none of the Scots he knows are interested in joining a Scottish military because the career prospects will be very poor compared to what they have in the UK military. An independent Scotland may very well find that young men and women minded to join the military will head south to join a world class military where they actually have a pretty good chance of doing the job they have trained for (remember Alex Salmond says an independent Scotland will NOT engage in the kind of military interventions the UK has in recent years).
Finally, there's the question of support contracts, all of which an independent Scotland will have to re-negotiate and fund for itself, and training. Scotland will either have to build its own training establishments, or (far more likely) send its recruits to rUK training establishments - which of course won't be free and neither should it be.
So it's not hard to see the dream of an independent Scottish military (and indeed independence as a whole) doesn't necessarily match up very well with the reality. An independent Scotland will be very much like Ireland and have no military of any real value but will instead continue to rely on rUK to guarantee its security.