DALLAS — Two major airlines reported huge second-quarter losses Thursday and warned that the recovery in air travel seen in April has stalled as coronavirus cases surge.

American posted a loss of more than $2 billion, and Southwest lost $915 million. That pushed the combined loss of the nation’s four biggest airlines to more than $10 billion in just three months.

Between them, American and Southwest carried 15.4 million passengers from April through June. A year earlier, more than 98 million people jammed on to their planes.

With all those lost ticket sales, airlines have turned to cutting costs and hoarding cash in a desperate bid to hang on until the shadow of COVID-19 passes.

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.

“However, the improving trends in revenue and bookings have recently stalled in July with the rise in COVID-19 cases,” he said. “We expect air travel demand to remain depressed until a vaccine or therapeutics are available to combat the infection and spread of COVID-19.”

Analysts believe the April-through-June quarter will turn out to be the industry’s low point. The recovery, however, is likely to be slow and uneven. United Airlines executives said this week that eventually they expect revenue to rise to 50 percent of last year’s level — they didn’t say when — and stay around that depressed mark until a vaccine is widely available.

Earlier, Delta Air Lines reported a $5.7 billion loss that was worsened by writing down investments in global airline partners who have filed for bankruptcy protection, and United lost $1.6 billion.

Some airlines are likely to lay off workers in October, when federal payroll help runs out.