Nextel Communications Inc., the Reston-based national cellular telephone company, reported a smaller-than-expected third-quarter loss yesterday, crediting its showing to record customer growth and higher-than-average revenue per customer.

Nextel posted a loss of $361 million, compared with a loss of $442 million a year ago. Analysts generally had expected Nextel to record a slightly larger loss in the recent quarter.

In an interview, Nextel's chief financial officer, Steve Shindler, said the best way to gauge the company's performance was not on its bottom-line loss but on its revenue growth and cash flow, both of which grew significantly.

"There are things we could do as a company to become net income positive in the short-term," Shindler said.

Shindler said he expects Nextel to move into the black over the next 18 to 24 months.

The market seemed to share that enthusiasm, adding $1 to Nextel's stock, which closed at $75.93 3/4.

* MicroStrategy Inc. of Vienna, a "data mining" firm, reported that its net income for the third quarter ended Sept. 30 was $3.8 million (9 cents a share), up from $1.9 million (5 cents) during the same period last year.

Revenue for the third quarter was $54.6 million, a 102 percent increase.

Net income for the nine-month period was $8.9 million (21 cents), up 160 percent. Revenue for the period was $136 million, up 92 percent.