Summer travel is booming. Airline investors are about to hear what happens next

Travelers arrive at main concourse of Denver International Airport in Denver, Colorado on Wednesday, July 7, 2021.
Hyoung Chang | Denver Post | Getty Images

Hordes of U.S. vacationers are back, crowding airports, filling up hotels and national parks. Airlines' second-quarter earnings should give some insight into what happens after the summer surge.