In Toronto and around the world there are two clear visions of how passengers should be moved by aircraft. The first is the Mega hub, an upsized version of the existing hub and spoke system in use at large airports since the 1970s. Pearson wants to become a mega hub. The second approach is called point to point , where passengers take a flight directly from an airport closer to their home, direct to a final destination.
Not to belabor the obvious, but passengers want point to point. No one wants to run around a mega hub ( looking like an expensive mega mall ) trying to find a connecting flight. It goes without saying that Smaller communities need to connect to larger airport for some flights, but new tech midsized airliners now have the flexibility, range and efficiency to make the majority of domestic and overseas destinations in one hop.
Discount Airlines are doing thier best to avoid mega hub airports by using more efficient smaller reliever airports for point to point runs. The reason is simple, operating costs. As congestion increases at the Hub airport, operating cost can increase dramatically with flight delays, long taxi lineup for take off and after landing for a gate.
A good example of a hub reliever pair is Heathrow and Standstead, or even Gatwick.
But the reliever airport must be close to or inside the hub passenger catchment area to work. This is why Pickering works for Toronto but Hamilton is challenged. But without a reliever airport, When the Hub airport is overloaded and runs out of slots it will upsize aircraft, cutting off service to smaller communities that are not economic for point to point and that the hub is actually best at serving. That is why allowing the Pearson monopoly to pursue its mega hub plan without an accessible reliever airport in Pickering is such a horrible idea.
See:
https://pickeringairport.org/how-pi...-a-winning-destination-for-low-cost-carriers/
Because of these factors the