* Netflix tumbles in premarket after quarterly results
* Initial jobless claims data on tap
* Futures off: Dow 180 pts, S&P 24.25 pts, Nasdaq 56.25 pts
By Chuck Mikolajczak
NEW YORK, Oct 16 (Reuters) - U.S. stock index futures tumbled on Thursday, after the S&P 500 closed at its lowest in six months, amid concerns about weak global demand and its potential impact on the U.S. economy and businesses.
* The S&P 500 and Nasdaq briefly fell into negative territory for the year on Wednesday as the S&P tumbled more than 3 percent to a session low, before rallying late in the session. The decline was also spurred by worries over the potential spread of the deadly Ebola virus and its possible impact on the travel industry.
* The benchmark S&P index has dropped in 6 of the past 8 sessions and is down 7.4 percent from a record closing high Sept. 18. The CBOE Volatility index is up 118 percent since the S&P record, and closed Wednesday at its highest since June 2012.
* Earnings reports did little to stem the equity rout. Netflix shares shares plunged 25.9 percent to $332.40 in premarket after it reported quarterly results and said it signed up fewer video-streaming subscribers than forecast for the quarter.
* S&P 500 companies expected to report earnings on Thursday include Goldman Sachs and Google.
* The earnings of S&P 500 companies are expected to grow 6.7 percent in the third quarter, according to Thomson Reuters data through Wednesday, on revenue growth of 4 percent.
* At 8:30 a.m. (1230 GMT), investors will eye weekly initial jobless claims data for insight into the health of the labor market. Expectations call for claims to rise slightly to 290,000 from the 287,000 in the prior week.
* At 9:15 a.m. (1315 GMT) industrial production data for September is due, while the NAHB/Wells Fargo Housing Market index and Philadelphia Fed's manufacturing business outlook for October are due at 10:00 a.m. (1400 GMT).
* Weakness in Europe continued, with the FTSEurofirst 300 index of top European shares dropping more than 2 percent to touch a 13-month low while Asian shares fell on worries about the global economy.
* S&P 500 e-minis were down 24.25 points, or 1.31 percent, with 464,261 contracts changing hands.
* Nasdaq 100 e-minis were down 56.25 points, or 1.5 percent, in volume of 63,711 contracts.
* Dow e-minis were down 180 points, or 1.12 percent, with 75,887 contracts changing hands. (Editing by Bernadette Baum)