Travel brands are adopting next-generation marketing tools, helping to persuade more of their current customers to splurge on extra products and services in their never-ending quest to boost revenue on the edges.

No prizes for guessing that airlines lead the way. Carriers famously sell more than tickets to fly. They long ago pioneered charging for nearly everything. Now, like other travel suppliers, they’re moving away from one-size-fits-all, open-to-everyone promotions.