* Indexes on track for third straight week of gains
* Priceline profit beats expectations, but outlook weak
* Futures up: Dow 64 pts, S&P 3.8 pts, Nasdaq 6 pts
By Ryan Vlastelica
NEW YORK, May 10 (Reuters) - U.S. stock index futures edged higher on Friday as the market's recent momentum returned, putting equities on track for a strong week that repeatedly took indexes to record highs.
* The S&P 500 ended a five-day streak of record closing highs, while the Dow broke a two-day streak by dipping modestly.
* The length of the recent rally has surprised many, and it may be difficult for the upward momentum to continue without further catalysts, such as first-quarter earnings reports, which are nearing an end.
* Still, investors expect shares to generally trend higher given the Federal Reserve's accommodative monetary environment and some encouraging data on the labor market.
* Boeing Co will be in focus a day after the company said it had succeeded in getting its factories to churn out 787 Dreamliners at a faster pace this week, a change that came sooner than expected and positions the plane maker to possibly deliver more of the high-tech jet than forecast.
* S&P 500 futures rose 3.8 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones (DJI: ^DJI - news) industrial average futures added 64 points and Nasdaq 100 futures rose 6 points.
* For the week, the Dow is up 0.7 percent, the S&P is up 0.8 percent and the Nasdaq is up 0.9 percent. It is the third week of gains for all three.
* Priceline.com Inc late Thursday reported first-quarter earnings that beat expectations, though its second-quarter outlook disappointed.
* With 89 percent of the S&P 500 having reported, 66.7 percent have topped profit expectations, above the average since 1994 of 63 percent. However, only 46.4 percent of companies have beaten revenue expectations, well under the historical average.