U.S. stock index futures were higher on Friday, a day after the S&P 500 ended at an all-time high and ahead of Federal Reserve Chair Janet Yellen's take on the economy that investors will peruse for clues on the timing of a rate hike. Yellen's speech at 1:00 p.m. ET (1700 GMT) is expected to acknowledge the recent economic sluggishness, including near stagnant performance in the first few months of the year. Before Yellen takes the podium, data is expected to show that consumer prices rose for a third straight month in April, signaling a rise in inflation, which could keep the Fed on track to raise rates. The Consumer Price Index data is due at 8:30 a.m. ET (1230 GMT). The S&P 500 ended at 2,130.82 on Thursday, barely beating its previous record close of 2,129.2 from Monday. While the Dow and the S&P are near record levels this week, trading has stayed in a narrow range and volumes have been subdued as the quarterly earnings season draws to a close. Aeropostale slumped 22.8 percent to $2 in premarket trading after the teen apparel retailer estimated a bigger-than-expected quarterly loss. ELong soared 35.8 percent to $28.04 after Expedia said it sold its entire stake in the Chinese online travel company to rival Ctrip.com and others. Ctrip was up 4.9 percent at $75.50.