U.S. stock futures higher after strong earnings reports

U.S. stock index futures were higher on Friday after three straight days of losses as Amazon, Visa and Starbucks beat expectations.

* Amazon.com (AMZN.O) shares jumped 18.3 percent to $570.56 in premarket trading, a day after the online retailer posted an unexpected quarterly profit.

* Dow component Visa (V.N) was up 4.7 percent at $75.15 after the credit and debit card company's results handsomely beat expectations.