What: Shares of No. 4 wireless carrier Sprint (NYSE:S) skyrocketed Tuesday morning, up by 19% as of 11:52 a.m. ET, after the company reported better-than-expected earnings.

So what: Net operating revenue came in at $8.1 billion, which all translated into a net loss of $0.21 per share by the time you reach the bottom line. While the top line was a little light compared to the $8.25 billion consensus estimate, Sprint lost less than the market was expecting. But more significantly, there are signs of progress with the turnaround.

Now what: Perhaps the most important figure was that Sprint added 366,000 postpaid phone customers, the highest level in three years and a major improvement from the 205,000 net postpaid phone customer losses it put up a year ago. CEO Marcelo Claure said that costs are coming down "faster than expected," as evidenced by the better-than-expected net loss. Sprint also raised its full-year guidance. Fiscal 2015 adjusted EBITDA was previously expected in the range of $6.8 billion to $7.1 billion, and Sprint is boosting that forecast to $7.7 billion to $8 billion.

Evan Niu, CFA has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.