Scotbill, this is thread drift I know, but I suspect that you drive north from the west side of the country and have not experienced the horrendous traffic jams at the Forth Road Bridge. Give it a try some time and you'll soon agree that a second bridge is very necessary.
As for the Edinburgh's trams, at least we have the comfort of knowing that the party we have elected to govern us at the last two elections were opposed to the trams. They were unfortunately out-voted by an unholy alliance of others.
Back to EDI v GLA. It's nothing to do with government influence and since the end of the time that governments were able to control the fine detail of where and when airlines flew it never has been. Edinburgh's growing dominance is down to two simple facts: a) location nearer to the centre of the country's population and motorway network, i.e. accessibility, and b) demand from incoming originating business - about 40% of total passengers, with a good mix of higher-yield business as well as leisure travellers, as opposed to Glasgow's predominantly outbound originating low-yield leisure business.
I worked for many years at both airports in a managent capacity. I am not biased towards one or the other. I look only at the facts and the reasons behind them.