U.S. stock index futures added to gains on Thursday after data showed the number of people filing new jobless claims fell sharply last week.

* Better-than-expected quarterly results from Alcoa Inc on Wednesday also gave a positive tone and eased some jitters over the second-quarter earnings season.

* S&P 500 futures rose 8.3 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 industrial average futures climbed 52 points, and Nasdaq 100 futures added 8.75 points.

(Reporting by Leah Schnurr; editing by Jeffrey Benkoe)