Fellows,

according to the RTW-Rules eff. 1st August 07 AC has removed the $250 surcharge for A345 flights YYZ-HKG vv. (since A345 does not operate AC15/16 any longer) but has now implemented a $250 surcharge for all 77L/77W flights

With AC's frequent aircraft changes on some routes (i.e. to and from LHR) I wonder how this works if your flight at time of ticketing shows 77W, you paid the extra $250 and at the gate waits an un-XM'ed A333 for you.