Stock index futures rose on Wednesday after forecast-beating results from Apple removed a weeks-old market overhang and lifted optimism in a corporate earnings season already outstripping expectations by a wide margin.

Industrial heavyweight Boeing Co and Caterpillar Inc also reported strong earnings early Wednesday.

Quarterly profit at Apple Inc , which dominates U.S. markets because of its size, almost doubled after a jump in iPhone sales. The stock had sold off recently, partly on fears earnings could disappoint. Its shares leaped 9.2 percent to $611.70 in premarket trade.

It has been a long time since I've seen one earnings report be so meaningful for the market, said Rick Meckler, president of investment firm LibertyView Capital Management.

The fact that they weren't the negative surprise that so many people feared will be a huge relief to this market and really could provide the impetus to bring it back to those previous highs.

The earnings season so far has been stronger than analysts expected. With results in from 153 S&P 500 companies, more than three-fourths have topped estimates, according to Thomson Reuters Proprietary Research as of Tuesday.

S&P 500 futures rose 9 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 gained 38 points, and Nasdaq 100 futures added 53 points.

The S&P 500 has fallen as much as 4.2 percent after running up about 30 percent from October to a 2012 peak in April. Fears about a resurgent debt crisis in Europe have been one of the main drivers of the pullback.

The cost to insure Spanish and Italian government debt against default fell as debt markets in the two countries looked more stable than in previous days, with traders citing buying from short-term investors.

The Federal Reserve will end a 2-day meeting later Wednesday. Fed officials may appear slightly more upbeat on the economy, but investors should not mistake cautious optimism for a desire to raise interest rates soon.

Boeing posted higher quarterly profit and raised its earnings forecast for the year. Caterpillar reported a 29 percent rise in profit.

Biotech company Amgen Inc will buy Turkey's Mustafa Nevzat Pharmaceuticals, a maker of injectable generic drugs, for about $700 million in a deal underscoring a thirst for emerging markets sales.

Amgen also posted better-than-expected profit late Tuesday and the biotechnology company bought back more of its shares. The shares rose 3.8 percent to $71.

Facebook Inc's journey to public markets may be delayed by about a week due to recent acquisitions, according to a source. It is buying photo-sharing start-up Instagram for about $1 billion and will pay $550 million for hundreds of patents from Microsoft Corp .

The Commerce Department releases March durable goods orders at 8:30 a.m. EDT (1230 GMT). Economists expect a 1.7 percent drop in orders, versus a 2.4 percent rise in February.

In the latest mergers and acquisitions, energy company Halcón Resources Corp said it will buy oil and gas driller GeoResources Inc for nearly $1 billion. GeoResources's shares were halted as the news emerged.

Nearly half of Mexico's state prosecuting authorities said on Tuesday they had no immediate plans to investigate allegations of corruption by Walmex, the Mexican arm of Wal-Mart Stores Inc .

Shares of Wal-Mart have slumped 7.5 percent since the allegations were reported by the New York Times last weekend. Walmex shares have lost nearly 15 percent.

European stocks <.FTEU3> rose 0.8 percent early Wednesday, extending the previous session's tentative recovery from 3-month lows after forecast-beating corporate results. <.EU>

(Reporting by Ed Krudy; editing by Jeffrey Benkoe)

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