Rising Covid cases hang heavily over the travel industry again. How to play the stocks now.

Royal Caribbean Group CEO Richard Fain was tempted to break into his company’s blog and sing “Oh, What a Beautiful Mornin'” in late June after the cruise line launched its first ship from U.S. waters since the pandemic sidelined the industry for more than a year. Fresh off that maiden voyage and with industry constraints thrown by the wayside, Fain gave an encore in mid-July and sang “I Can See Clearly Now.”

Not so fast, says the Delta variant. As the mutated Covid-19 strain has been spreading for months,…