Apple stock is on track for a second day of gains following the news from two major U.S. carriers that iPhone 7 preorders were through the roof for just the first three days they were taken. The news was a welcome surprise as Apple said when it launched this year’s iPhones that it would not be releasing first-weekend sales because the initial supply is limited and it expected to run out quickly. It also confirms the multiple analyst reports that proclaimed the iPhone 7 “good enough” to trigger upgrades.

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Needless to say, analysts from multiple firms were crooning over the reports, and Apple stock bucked the broader trend that dragged other U.S. equities lower. Even Apple’s huge heft and small stock price increase was only good enough to barely keep the S&P 500 in the green in early trading.

Sprint, T-Mobile report massive sales of iPhone 7

On Tuesday, Sprint and T-Mobile both released details on the preorders they took for the iPhone 7, which began on Friday. Sprint said preorders for this year’s model surged more than 375% year over year for the first three days.

T-Mobile’s news was even better, as it said preorders almost quadrupled compared to the “next most popular iPhone,” which is probably the iPhone 6, although the carrier did not elaborate beyond that language. The mobile carrier said the iPhone 7 and 7 Plus “shatter[ed]” past records for iPhone preorders on its network and that pre-registrations also broke the past record.

No word from Verizon or AT&T about the iPhone 7

One thing that should be noted is that Verizon and AT&T stayed mum on the topic of iPhone 7 preorders. As a result, we must take into consideration how many of these preorders were from people who are switching mobile carriers. This is especially true for T-Mobile, which has been growing rapidly compared to its three main competitors. It’s possible that the carrier managed to attract subscribers away from Verizon, but we won’t know for sure until the earnings reports start rolling in.

Analysts have also been advising investors not to write off the iPhone 7 due to its lack of new features and the expectations for a much bigger upgrade next year. The reason is because this year marks two years since the massive iPhone 6 release. Also those who bought the iPhone 6s on Apple’s annual upgrade program are probably upgrading just because they can. Of course it doesn’t really matter where the company gets its iPhone sales from. All that matters is that it sells enough phones to please investors.

iPhone installed base impact could boost Apple stock

Stifel analyst Aaron Rakers said in a report dated September 13 that he believes investors will see these reports from Sprint and T-Mobile as indicating just how big the impact from the expansion of Apple’s huge iPhone installed base has been over the last few years. He estimates that the installed base stood at around 675 million iPhones at the end of the June quarter, which is a massive increase from the roughly 200 million he estimates for before the release of the hugely popular iPhone 6 two years ago.

Rakers said previously that second quarter postpaid iPhone upgrade rates sat at their lowest level since 2013 during this year’s June quarter. He also noted that there will be nine days of iPhone 7 orders going toward the September quarter this year, compared to only two days with the iPhone 6s last year. Also this year’s model launches in more than twice as many countries at the beginning compared to last year’s model.

Of course Apple stock is greatly affected by iPhone sales and has been for many years, as it struggled in 2013 due to the slow sales and clearly is receiving a boost now from the preorder news from Sprint and T-Mobile. Shares of Apple stock surged by as much as 3.01% to $111.19 in morning trades on Wednesday.