I often visit this thread in the hope that I might hear news of new services from Teesside; I'm clearly either an eternal optimist or addicted to disappointment.
There is, of course, no way that Teesside can relieve pressure on Heathrow. However, those pushing for extra capacity at Heathrow need to realise that while a big airport means lots of flights, good connections and numerous destinations to choose from, there is a point at which a big airport becomes too big. Planes stacking to land, queueing for take-off and waiting for bus transfers mean that passengers miss connections, baggage gets delayed, and journey times get extended as the time it takes to transfer gets longer and longer. When this happens, it is time to stop growing and consolidate.
Every hub airport depends on two things: A good basis of local traffic, and a good network of destinations. If Heathrow's catchment area generates enough yield to justify three flights a day to Warsaw, and transit passengers enough to justify two more, then they all benefit from the convenience of having five flights a day. That in itself generates employment. The crazy thing is that some of those passengers will have travelled from Lincoln, Middlesbrough or Chesterfield to London by train, then across London by Tube, adding to the capital's public transport congestion; others will have come by car from Kent, Oxfordshire or Dorset, adding to traffic on the South East's busy motorways.
The point is that Heathrow does not just serve West London and Berkshire. People travel there from all over England and Wales because of an historic lack of alternatives. The advent of the Locos in the last twenty years has shown that there is (both existing and generated) demand from the regions; but the high yield (mainly business) traffic has continued to be London-centred.
All Teesside has to offer is a long runway, and a small catchment population. However, as a 'UK gateway' it offers as much as any other. Two examples: A Japanese business visitor with appointments in Leicester, Swindon, Preston and Newcastle could enter at any point on that circuit, particularly if there was a direct flight to Amsterdam from their Japanese regional city; likewise an American tourist doing a tour of the country could start and finish at Edinburgh or Birmingham (or Dublin!) and still include London without having to queue for hours at Heathrow immigration.
If Teesside and some other regional airports were to get together (instead of directly competing) and market themselves to airlines and passengers as 'gateways to the UK', then perhaps some of the pressure currently being suffered in South East England could be averted.