Originally Posted by
Seat 2A
28. (2001) There’s no easy way to get from Kona, Hawaii to Montreal, Quebec but on a positive note you’ve found an interesting routing involving three nonstop flights, each operated by a different airline with each utilizing an aircraft type built by a different manufacturer. Additionally, there’s one more similarity between each aircraft type that would not apply with any other trio of aircraft types possible between this city pair. Can you identify the route, the three airlines and the three aircraft types? The admiration of your peers will rise inestimably should you also be able to acknowledge the unidentified similarity between each aircraft type.
I can come up with a handful of possible routings for this trip; as there are a pair that might meet an "unidentified similarity" criterion, I need to eliminate one of them. The criterion is "size matters" -- referring to the smallest range-capable jet in the fleet operating the segment
We could start out with KOA-Honolulu/HNL on a Hawaiian DC-9-50 followed by HNL-Toronto/YYZ on a Canadian International 767-300, or KOA-Los Angeles/LAX on a United 757 and LAX-YYZ on an Air Canada A319; the last flight in each instance is a Canadian Regional F.28 YYZ-YUL. I'm leaning toward the LAX routing simply because one could consider Canadian International and Canadian Regional parts of the same airline, and we all know those sort of technicalities carry significant weight here 
Hawaiian is correct between Kona and Honolulu. The rest of your answer - DC-9-50, LAX, YYZ, United 757 and AC 319 are all incorrect. Additionally, the similarity factor has nothing to do with size. The quest for admiration amongst your peers - at least insofar as this question goes - continues.
28- another route possibility is KOA-HNL HA DC-9-30, HNL-Newark/EWR Continental 767-400, EWR-YUL AC CRJ-200 -- but beyond the fact that all are twinjets, the unidentified "similarity between each aircraft type
that would not apply with any other trio of aircraft types" escapes me here (esp because one could probably construct something like HNL-YVR-YUL, Canada 3000 A330 connecting to AC A320 or CP 767-300, but those would both violate the "three different manufacturers" condition)
changing to HA 717 would perhaps open "newest member of the airline's fleet" but we would have to consider its original MD-95 type designator (speaking of "technicalities")