U.S. stock index futures were subdued on Thursday ahead of fresh economic data that could offer clues on the Federal Reserve's monetary tightening plans, while investors also waited for earnings from big banks after turmoil in the sector last month.Market SnapshotAt 8:10 a.m. ET, Dow e-minis were flat, S&P 500 e-minis were up 2.5 points, or 0.06%, and Nasdaq 100 e-minis were up 16.75 points, or 0.13%.Pre-Market MoversDelta Air Lines (DAL) reported first-quarter adjusted earnings of 25 cents a share, missing analysts’ estimates, but the carrier said its outlook for the second quarter was “strong” and added it was “confident” in full-year guidance for revenue growth of 15% to 20%. Delta shares rose 3.7% in premarket trading.The report from Delta follows a lukewarm earnings outlook from A