Realize I've clearly given some erroneous YQ calculation info - sorry! I'm still unclear on how it IS calculated though.
Say I go YVR-YUL(AC)/YUL-ZRH(LX)/ZRH-IST(TK) and then return the same way - I understand those in the know are saying YQ is calculated for a origin and destination of one YVR-IST flight; but on which airline?