iPhone5-34Flat-iOS7_PRINTThe latest U.S. smartphone market share numbers from Kantar show Apple gaining ground on rival Android.

While Google still led the way with 52 percent of the market, Apple’s iOS share increased 3.5 percent to 41.9 percent in the three-month period ending in May, compared to just a 0.1 percent growth on Android.

Windows Phone, meanwhile, remained in third place among U.S. smartphone sales with a 4.6 percent share, which is down one percent from last month but up 0.9 percent from the same period last year.

Apple can thank T-Mobile USA for the recent increase in iPhone owners. The Bellevue-based carrier finally began offering the iPhone 5 in April and it quickly became its best-selling smartphone in the March-to-May timeframe, according to Kantar.

T-Mobile featurephone owners who waited to make the shift to smartphone played to Apple’s favor. Kantar’s Dominic Sunnebo said that 53 percent of T-Mobile iPhone owners previously owned a featurephone, up from the market average of 45 percent.

tmobile1111T-Mobile, which recently acquired MetroPCS, said it sold 500,000 iPhones less than a month after the phone’s debut in April. The iPhone was offered as part of T-Mobile’s, “Uncarrier” payment plan, which separates the cost of wireless service from the purchase of a phone — no longer subsidizing the cost of the device as part of the service plan.

iPhone customers were able to pay $99.99 down and then fork over $20/month for two years — for a total of $579 — to complete the purchase of the smartphone. However, T-Mobile bumped the initial payment up $50 in May, which actually boosted the total price of the smartphone in the process.

Despite the impressive iPhone numbers, revenues for T-Mobile still fell seven percent during the first quarter. The carrier remains in fourth place in terms of smartphone sales at 10.1 percent, down 3.4 percent from the same period last year. Verizon is in the lead at 34.6 percent, AT&T is second with 29 percent and Sprint is in third at 12.7 percent.

Previously on GeekWire: T-Mobile customers wait in line, swap Androids for iPhone 5

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