The Apple Pay mobile-payments service is generating 15 billion transactions a year, and Apple Inc.’s new Apple Card helped lift sales of the company’s flagship product, the iPhone, Apple chief executive Tim Cook said Tuesday.

“For Apple Pay, revenue and transactions more than doubled year-over-year, with a run rate exceeding 15 billion transactions a year,” Cook told analysts during the Cupertino, Calif.-based company’s conference call for fiscal 2020’s first quarter ended Dec. 28. As usual, Cook didn’t give numbers, but payments researchers regard Apple Pay, launched 2014, as the most popular of the U.S.-based mobile-payment services.

Cook said mass transit is a fast-growing market for Apple Pay, with contactless payments through the service enabled on the vast Transport for London bus and subway system. More Chinese cities going live with Apple Pay, including Shenzhen and Guangzhou this spring. U.S. transit systems accepting Apple Pay currently include Chicago, Portland, Ore., and some New York City locations.

Apple Pay is part of Apple’s services unit that includes its subscription-based businesses, including the new Apple TV+ service. Quarterly services revenues grew 17% year-over-year to $12.7 billion to account for 14% of the first-quarter’s total sales of $91.8 billion, a 9% increase.

Meanwhile, the Apple Card, a Mastercard launched in August by issuer Goldman Sachs Group’s consumer unit, fulfilled one on its assignments by spurring sales of the iPhone smart phone during the holiday shopping period. U.S. customers using the card in an Apple store or online to buy an iPhone could repay in 24 monthly installments. Cook didn’t disclose how many customers took advantage of the offer, but he said “we are thrilled with the continued growth of Apple Card.”

Goldman Sachs reported earlier this month that it provided $2 billion in loans in 2019’s fourth quarter through the Apple Card, according to an earnings call transcript from SeekingAlpha.com.

Apple recorded iPhone sales of $56 billion, up 8% from $52 billion in fiscal 2019’s first quarter. Net income rose 11% year-over-year to $22.2 billion.