S&P 500 stock index futures briefly turned positive before again turning lower on Friday as investors prepared for the start of earnings season next week.

S&P 500 futures fell 0.3 points but were still 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 fell 17 points, and Nasdaq 100 futures lost 2.8 points.

(Reporting by Edward Krudy, Editing by W Simon)