Is there an advantage / disadvantage of scheduling flight with VIA option?
If I have a hub in JFK and I schedule a flight CLT JFK YYZ do I just capture the customers flying CLT YYZ or do I tap in to the local OD market as well?
Does this shorthen the turn around time in JFK ?
Thank you
Passengers can enter in JFK also. If you stay minimum transfer time on the ground, you can also let connecting passengers enter the plane. TA times are same as no via-flights.
There’s absolutely no advantage I’m using VIA flights, except for special traffic rights with the Yamoussoukro Decision & Caricom 5th Freedom treaties.
So for you operating in the US, you can just stick to regular flight numbers.
A similar question:
Origination from A, Via point B, and Destination C. Both B & C are small airports that are transfer impossible. If I schedule 2 regular flights, A-B & B-C, since B cannot transfer pax, there is no passenger from A to C. However, if I schedule a via flight A-B-C, can I capture both A-C and B-C?
Even for that you won’t need a VIA flight - when it’s the same aircraft continuing to the next flight, passengers and cargo can always stay on board and won’t need to care about transfer ability or transfer time of the airport.
The reason to use VIA flights is that you can operate 3100 aircraft with just 10,000 flight numbers like YTJET.
There seem to be different aims for some players. 
From my point of view that makes no difference. Handling of via flights is a bit more complicated and if your ego does not need to be in number 1 statistics there is no reason beside the traffic rights Specialist mentioned. What a workload for nothing.
I may add one very special case where VIA is about the only option:
Airline running out of flight numbers operating a hub outside of its legal home where a sub can’t take the job due to traffic rights.
If so, if I understand it correctly, when I schedule a filght from country A to country B to country C, or from country A to city X of country B to city Y of country B, even I don’t have special treaty (e.g. 5th freedom) nor via flight, as long as I use same plane, I can effectively transfer my pax to the final destination?
If there is no treaty in place, lets assume country A is your legal home country, B & C are not in your legal home country…
You can plan a flight, either as a via, or as two separate flights (it does not matter) from A > B > C. However passengers can only book A>B or A>C. They cannot book B>C
Using a real example. My company is based in the USA. I plan a flight from LAX>MEX>CUN, or LAX>MEX>LIM. In both options passengers can book LAX>MEX, LAX>CUN, or LAX>LIM. Passengers cannot book MEX>CUN, or MEX>LIM