There was no benefit to Leeds and Liverpool from the time when Manchester had a de facto monopoly on civil air transportation in the north. Older people will remember that it was favoured with a second runway in preference to Liverpool's aspirations, on the grounds that it had the potential to provide a gateway role. But it has entirely failed in providing that role, not because of the "nibble" or "tertiary" airports but because there was no need for such an airport in the North of England. The model was flawed.
What Leeds and Liverpool needed were good quality airports that were able to grow - and once the market was allowed to operate we saw in Liverpool's case just how much "captive" traffic and growth Manchester had. It leaked away because people didn't want the hassle of going to Manchester. Liverpool's catchment is, according to some fascinating CAA maps, very very similar - so once it is able to establish long-haul routes the market will be pretty much the same.
The particular need Liverpool has is direct connections to Heathrow, although the new KLM Amsterdam service will do for now. That was an important priority for Greater Liverpool's economy.
I'm afraid the fact is that a lot of Greater Liverpool people just don't like going through Manchester, they prefer their own regional airport, and good access to the national hub in Heathrow. I know people who live in parts of what is "officially" Greater Manchester, for example a mate in Wigan, who finds Liverpool more convenient and prefers to use it.
Manchester's economic development industry have claimed for years that they have a unique competitive advantage in the north because of their airport - so how come that Manchester airport can in one sense favour Manchester (eg in attracting inward investment) and at the same time favour the very cities it is competing with (eg Leeds and Liverpool)? It's nonsense to argue it both ways.
Manchester has failed to establish itself as a hub and failed as a "gateway". The industry changed around it. It isn't a hub, it isn't a gateway, and it can't become one. It's time to move on from that. The priority now is good links, preferably rail, to Heathrow, and building up good quality regional business services out of Liverpool, Leeds and other airports.
I would like to see Manchester de-designated as a "gateway" in the strategic plans of the North West and the Northern Way. It is an entirely unhelpful designation that may flatter a few provincial egoes in that town, but does nothing to build the connectivity of the north to vital business centres. I want to see Liverpool Airport achieve its full potential, competing head to head with Manchester on long haul in the future, and linked into high speed rail that will provide Greater Liverpool businesses with quick journey times to Heathrow.