Driven by strong results from its prepaid Boost Mobile unit, Nextel saw an 810,000 net subscriber increase in the first quarter, ending March with more than 17 million customers.

The company's overall earnings suffered, however, as Nextel recorded $589 million in net income, down from $593 million in the first quarter. Those reduced earnings numbers also included tax benefits Nextel received in the first quarter. Those benefits excluding Nextel's profit were $444 million.

The carrier's overall revenues continued to climb, however. Nextel posted $3.61 million in revenue, up 16% over last year's $3.1 billion in Q1 revenues, and the company achieved its best-ever Q1 churn rate at 1.5%.

While youth-oriented brand Boost Mobile accounts for only a small percentage of Nextel's overall business, it's rapidly growing. Of its 810,000 net adds last quarter, 314,000 were Boost additions. Boost now has 1.5 million subscribers as Nextel continues to expand the service nationally. The brand's subscribers have more than doubled in a year.