Chase UR is good when buying coach (on any airline) or buying business on an airline like UA that doesn't offer InsiderFare savings.
I always like to keep a large AMEX MR balance for easy (online, self-service) and fee-free access to discounted business InsiderFares on AS, AA, DL.
If you don't have the AMEX Biz Plat or you don't have sufficient points, then you have to call Plat Travel to book with an agent and pay the $39 ticketing fee.