NEW YORK, March 21 (Reuters) - Even as U.S. stocks seek to regain their footing, weakness in a closely followed index of transportation shares is a sign of growing investor worries about the economy.
The S&P 500 (.SPX), opens new tab as of Thursday was on pace to post a weekly gain after four straight negative weeks. The benchmark index was clawing back after it marked a correction last week by ending down over 10% from its February record high.