Stock index futures pointed to a flat open in what could be a volatile session on Friday after Wall Street recorded three straight winning days and as investors braced for the start of earnings season next week.

Most of the gains in the holiday-shortened week, marked by volatility and low volume, were driven by hopes that U.S. corporations will post strong quarterly results when Alcoa Inc starts reporting season on Monday. Alcoa's shares, a component of the Dow index, edged up 0.4 percent in premarket trade.

Early volatility in the futures market suggested Friday's trading could also be choppy. Even so the S&P 500 was on course for its best week this year.

Google Inc shares jumped 2.7 percent after it said the Chinese government renewed Google's website license, averting a shutdown of its search page in the world's biggest Internet market. Shares of local rival Baidu Inc fell 3.2 percent.

Sentiment remained fragile going into the Friday session, with many investors concerned the global economy could slip back into recession. Even with the gains of the last three days the S&P 500 is still down 12 percent since April and down 4 percent this year.

However, Subodh Kumar, chief investment strategist at Subodh Kumar & Associates in Toronto, said this week's market action had been constructive with the S&P 500 holding around the 1,050 level.

The next few days they'll be two things two watch: one is the earnings as they come through and the second is news from Europe as it comes through on the stress tests, he said, referring to tests in Europe to assess the strength of the region's banks.

S&P 500 futures fell 1.3 points and were below 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 fell 17 points, and Nasdaq 100 futures fell 5.5 points.

Friday's data includes U.S. wholesale inventories for May at 10:00 a.m. Economists in a Reuters poll expect inventories rose for a fifth straight month but will watch the inventory-to-sales ratio, a gauge of how long it takes to sell goods, after it previously hit the lowest on record dating back to 1992.

U.S. data showing slowing growth in the services and manufacturing sector, weakness in housing and a stagnating jobs market has worried investors, although most say it is too early to call a double-dip recession.

If there is some kind of double-dip out there to be had I don't think it's imminent, I'm not saying there's a 90-percent chance - there's a 50-percent chance, said Kim Caughey, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.

Equity funds worldwide suffered more than $11 billion in net outflows in the first week of July, while money market funds saw the biggest inflows in 18 months amid fears of a double-dip recession, fund tracker EPFR Global said.

(Reporting by Edward Krudy; Editing by Padraic Cassidy)