Porter does what it does well - and their competition with AC Jazz/Express is big reason why I was able to justify going Sault Ste. Marie early last month. (I've also flown to Timmins, Dulles, Ottawa, Midway, and Newark on Porter.)
Yes, and it's important to underscore that many of Porter's destinations are ones that Air Canada couldn't really care less about. Sault Ste. Marie, Timmins, Thunder Bay and even Quebec City are good examples of those. Air Canada basically "let them have it".
But AC is absolutely not going to roll over and let Porter take the vital Toronto-Vancouver route. Apart from sizable domestic traffic, that route is very important in both directions from an international connections perspective: for Torontonians heading to Asia via Vancouver, and for Vancouverites heading to Europe and Latin America through Pearson. People flying in from Asia are simply not going to buy an extra ticket and pay an additional $500 to transfer to a Porter flight at YVR.
Similarly, LAX, SFO and MIA are important international hubs, and I think a lot of Torontonians fly
through these airports, rather than
to these airports.
I also don't think Porter has much of a chance with the Toronto-Calgary market. Again, Calgary is an important Westjet and Air Canada hub for service to Western Canada's regional centres, and Porter won't be able to compete unless it creates a second, regional airline for Western Canada.
What's left? Some sun destinations. People who want to fly to Cancun or Orlando are typically budget travellers and families with a lot of luggage who don't live downtown, anyway. I don't see Porter appealing to them.
I have never really seen a true value in pre-clearance of US customs.....at some point in your journey you are going to have to line up to clear customs......whether it's in Toronto or Seattle....it does not make much of a difference. (IMO)
Apart from what Jay said, the other value in pre-clearance is that you can fly to US airports that don't have international traffic. Places like Columbus, etc.
For me, pre-clearance is all about managing my time. I would much rather wait in line before my flight departs than arrive late to a destination and get further squeezed by having to wait in line for customs.