The fresh spike in jet fuel prices in July upended the profit guidance of U.S. airlines, whose management teams had to readjust earnings estimates for the year just days ahead of reporting second-quarter results. The re-escalation in the Middle East earlier this month resulted in a 20% spike in jet fuel prices during the two weeks in which air carriers were reporting their April-June earnings and attempting to guide earnings for the third quarter and the rest of the year. The extreme volatility in crude oil and consequently, jet fuel prices,…