DALLAS — Two major airlines reported huge second-quarter losses Thursday, and their leaders warned that the new surge in U.S. coronavirus cases has stalled the recovery in air travel and added to their industry's disarray.

American Airlines posted a loss of more than $2 billion, and Southwest Airlines lost $915 million. That pushed the combined second-quarter loss of the nation's four biggest airlines to more than $10 billion.

Southwest CEO Gary Kelly said he was encouraged by a pickup in leisure travel during May and June after the dark days of March and April. Southwest added flights for July and August.

Then in the last few weeks a surge in U.S. COVID-19 cases caused bookings to fall, Kelly said. Southwest rewrote its August schedule, dropping some flights.

“We're just going to have to be prepared to have a lot of volatility and be prepared to make frequent adjustments,” Kelly said, “because it's really almost impossible to plan right now.”

Business did improve for McDonald's throughout the second quarter as restrictions lifted across the globe, but the fast food giant faces a bumpy — and expensive — recovery.McDonald's President and CEO Chris Kempczinski said the coronavirus pandemic continues to cause uncertainty and depress consumer sentiment But he believes the April-June period will be the trough in the company's performance.“McDonald's has learned to adjust our operations to this new environment,” Kempczkinski said Tuesday in a conference call with investors.Of the chain's 39,000 restaurants worldwide, 96 percent are now open, compared with 75 percent at the start of the second quarter. Comparable-store sales that were down 39 percent in April were down only 12 percent by June.

Boeing lost $2.4 billion in the second quarter and the company will slow production and cut more jobs as demand for commercial aircraft shrinks during the coronavirus pandemic.The loss was far worse than Wall Street expected; so was the decline in revenue, which fell 25 percent.“The reality is the pandemic's impact on the aviation sector continues to be severe,” CEO David Calhoun said. He said airlines are delaying purchases, slowing down deliveries and deferring elective maintenance, “all of which affects our business and, ultimately, our bottom line.”With interest in new planes fading, Boeing said Wednesday it will slow its production of the 787 and 777 models and delay the introduction of a new big plane, the 777X, by a year until 2022. The company will study whether to close one of its two factories that make the 787.