By Lisa Barrington and Jack Queen (Reuters) -Airlines on Monday were weighing how long to suspend Middle East flights as a conflict which has already cut off major flight routes entered a new phase after the U.

Despite Iran’s Security Council threatening to close the Strait of Hormuz, a vital artery for 20% of global oil, U.S. markets remain surprisingly calm. Dow Jones and S&P 500 futures are slightly up, and the VIX, a measure of market volatility, dropped 3.4%, signaling confidence.