"They've made the decision to pull away from the American Express partnership, which is obviously disappointing to our cardholders," said Sravanthi Agrawal, vice president of public affairs.
Read MoreAffording a no-interest credit card offer
"There definitely have been some major hits," said Brian Kelly, founder of ThePointsGuy.com. "Platinum still has perks, but it is harder for some people to justify. You really have to piece together and say, how much value am I really getting?" That reassessment is necessary for all credit cards with an annual fee, but particularly when the card in question costs $450 a year.
Just days before the American and US Airways lounge cutoff, American Express announced two new benefits for platinum members: unlimited global access to land-based Wi-Fi via Boingo (worth about $60 per month) and an $85 credit to cover the application fee for TSA Pre-Check. (Cardholders were already entitled to a $100 credit for Global Entry program application, which extends eligibility to Pre-Check.) Both target pain points consumers have complained about—namely, slow or expensive Wi-Fi, and long airport security lines, said Agrawal. "American Express is committed to enhancing card-members' travel journey," she said.
The issuer is also in the process of boosting lounge access, with its own brand of Centurian Lounges featuring free amenities including a craft cocktail menu, buffet of seasonal fare and quick spa treatments.
Read MoreAs the mile gap widens, new flier loyalty tactics
"We think of all of this as, we want you to have a nice experience that makes your travel enjoyable," Agrawal said. Locations in Las Vegas and Dallas have opened in recent months; spaces in San Francisco and New York's LaGuardia are in progress. Cardholders also retain some longstanding perks there: access to partner Delta lounges (which regularly costs $695 per year), and membership to lounge network Priority Pass ($249 per year).