Originally Posted by
armagebedar
When searching for carrier-specific and IATA normal fares, I've noticed that carriers will often issue two fares (e.g. two C fares) with the exact same rules at very different prices. When I try to construct an itinerary using said fare in ITA, invariably the higher fare is used. (Nothing is returned when I try to force the lower fare basis to be used.)
Why are multiple fares displayed like this in EF, and why would a reservation system ignore the lower fare?
Did you check for differences in the routing rules? Are you comparing 2 YY fares or a YY fare to a carrier fare? Carriers don't issue YY fares, they are common to all applicable carriers.