In other news:
* The Federal Reserve begins its two-day open markets committee meeting.
* World leaders meet at U.N. headquarters in New York for a one-day climate summit.
Light on earnings and economic data, equity markets may be volatile on this quadruple witching day.
* Friday marks the quarterly expiration and settlement of four different types of September equity futures and options contracts. The “quadruple witching” can lead to greater volume and volatility as players adjust and exercise derivative positions.
* FedEx reports fiscal first-quarter earnings before the bell. The package delivery giant is expected to benefit from stabilizing freight volumes as well as lower fuel prices.