Stock index futures advanced on Wednesday and pointed to a higher open, after data from China and Boeing provided temporary relief to a slumping market, and following declines Tuesday when the Dow suffered its biggest drop in four months.

The S&P 50 has dropped more than 3 percent over the last four sessions, as weak earnings outlooks and top-line revenue misses by large multinational companies reignited worries about a slowing global economy.

The China HSBC Flash Manufacturing Purchasing Managers Index (PMI) showed that growth shrank for a 12th straight month in October, but output was at a three-month high of 49.1 and order books at their most robust since April, signaling a strengthening recovery.

Boeing Co shares climbed 2.5 percent to $74.65 in premarket trading after the commercial jet and defense giant reported earnings and raised its full-year 2012 outlook.

That optimistic outlook bucked a recent trend by companies with a large global footprint - including DuPont , United Technologies Corp and 3M Co - of lowering their full-year forecasts.

"At the end of the day - we've been through this for three years - the short term bumps that Bernanke is providing is just a sugar high, and fundamentals matter," said Seth Setrakian, partner and co-head of U.S. equities at First New York Securities in New York.

"He's probably prevented it from being worse but stocks are based on valuation, based on their earnings and projected future business and the economy is slowing and prices are reflecting that."

A total of 43 S&P 500 companies are scheduled to report earnings on Wednesday, including Citrix Systems Inc , F5 Networks Inc and Symantec Corp after the close.

AT&T Inc posted third-quarter revenue that was below analysts' expectations, but its earnings increased from a year earlier. Shares were unchanged at $35 in premarket trading.

Dow Chemical Co , the largest chemical maker in the United States, said Tuesday it would cut 5 percent of its workforce and shut 20 plants to counter a slowing global economy. Its shares advanced 5.6 percent to $30.14 in premarket trade.

Eli Lilly and Co shed 2.4 percent to $50.65 after the drugmaker reported quarterly earnings and sales below Wall Street expectations, hurt by higher taxes and generic competition for its Zyprexa schizophrenia drug.

S&P 500 futures rose 7.1 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 added 49 points, and Nasdaq 100 futures added 15.25 points.

Facebook Inc surged 26.7 percent to $24.72 in premarket after the social networking company grew mobile advertising revenue several times in the third quarter, a faster-than-expected pace.

EMC Corp lost 1.9 percent to $24.20 in premarket trading after the data-storage equipment maker cut its full-year outlook on Wednesday and reported third-quarter sales and earnings below analysts' expectations amid reluctant customer spending.

With results in from 29 percent of S&P 500 companies, 37 percent have exceeded revenue forecasts, far below the 62 percent average, and just 57.2 percent of the S&P 500 names reporting so far have beaten earnings forecasts, according to Thomson Reuters data through Tuesday morning.

The current reporting season has seen the lowest percentage of companies exceeding estimates since the fourth quarter of 2001.

Financial information firm Markit said its U.S. "flash," or preliminary, Purchasing Managers Index for the manufacturing sector edged up to 51.3 this month from 51.1 in September, but slow growth and economic uncertainty suggested the sector's recent struggles may persist over the final months of 2012.

At 10:00 a.m. (1400 GMT), investors will peruse September new home sales and the August home price index for continued signs the industry is returning to health.

Economists in a Reuters survey expect new home sales to show a total of 385,000 annualized units, compared with 373,000 in August. The home price index had risen 0.2 percent in July.

The Federal Open Market Committee will conclude the second day of a two-day meeting on Wednesday. Analysts and primary dealers expect the FOMC to leave fed funds rate in the current 0.0 percent to 0.25 percent range.

(Editing by Bernadette Baum)