Activist investor Daniel S. Loeb, who runs hedge fund Third Point LLC, disclosed a new long position in American Express (AXP).

In a new letter to investors, Loeb argues that the credit card giant could see its shares trade above $135 over the next 18 months, a 30% upside. Shares of American Express were last trading around $108 on Friday afternoon.

According to Loeb, American Express, right now, is “a franchise that appeared to lose its way in recent years.” He highlighted the company’s loss of co-brand relationships with JetBlue (JBLU) and Costco (COST) as recent examples of lost business to competitors like Chase’s (JPM) Sapphire Card. As a result, the stock has underperformed the SYP 500 by about 40%.

“We think this challenging period galvanized the franchise, forcing necessary investments and a strategic pivot that is just beginning to pay off,” Loeb wrote. “New CEO Stephen Squeri is re-energizing Amex by focusing on topline growth and under-appreciated structural opportunities in Commercial and International — efforts we think will lead to more sustainable double-digit EPS growth going forward.”

Among those efforts are customer acquisition, card acceptance, and higher average spend. Loeb noted that Millennials are now half of the Platinum card’s customers. What’s more, the merchant acceptance of American Express is growing at a “high single‐digit pace, twice that of Visa/MasterCard.”

Another part of the story is the growth in international and commercial, especially since American Express has relationships with about 60% of global Fortune 500 companies and is gaining share among smalle medium enterprises. According to Loeb, Wall Street is missing this.

“While Wall Street tries to find the next high‐multiple stock to monetize the shift in B2B payments – an area with ~$20 trillion of addressable spend and ~10% penetration – they are missing a more obvious beneficiary in American Express, where B2B already makes up 2/3 of commercial spend. No one is better equipped to monetize the opportunity than Mr. Squeri, who previously ran Amex’s Commercial division. The recent partnership with Amazon to offer co‐brand cards to small businesses is testament to Amex’s positioning in the commercial market.”

This story is developing…

Julia La Roche is a finance reporter at Yahoo Finance. Follow her on Twitter.

• Bill Ackman reveals $900 million long position in Starbucks