United Airlines customers outraged over the passenger removal video are literally cutting ties with the airline.
While some social media users took to Twitter to call for a full-on boycott of United Continental Holdings ual , others posted photos of their cut-up United MileagePlus credit cards—a loyalty program that’s otherwise been highly lucrative for the airline.
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Customers in the U.S. weren’t the only ones canceling their cards, which are provided by Chase: One user on the Chinese social media platform Weibo announced Tuesday that they would no longer use the card despite having been a customer for five years.
“It’s true,” the user wrote, “If that doctor had not been a Chinese person living abroad, maybe I wouldn’t have cancelled the card.” (Fortune was unable to confirm that the passenger removed, Dr. David Dao, was in fact Chinese.) The person added that canceling the card was a form of protesting how United treated the passenger.
United’s credit card partnership with Chase has become an increasingly important part of its operations, according to Stifel airline analyst Joseph DeNardi. The airline makes a profit by selling miles to the bank at a high price. Chase then distributes those miles to its customers, who pay an annual fee for the card.
But angry United flyers demonstrated on social media this week the various ways they were shredding their credit cards, a reaction reminiscent of the recent #DeleteUber campaign among disgruntled customers of the ride-hailing company.
While United doesn’t disclose how much it earns from its loyalty programs, groups such as IdeaWorks closely study airlines and their ancillary revenue. By IdeaWorks’ estimates, United’s programs accounted for 8% of the company’s total revenue in 2015, with the majority of that near $3 billion revenue coming from from activities related to its Chase co-branded credit card.
The program is also highly profitable, with the loyalty program generating profit margins somewhere in the 60-70% range, according to DeNardi’s estimates. DeNardi also thinks that Wall Street has largely underestimated the value of the program, and believes United’s loyalty program could be worth even more than the company at its current market cap of about $21 billion.
While consumers in some regions will be unable to avoid flying United, they do have a plethora of credit cards to choose from.