Airlines will likely suffer more disruptions like the one that grounded about 2,000 Delta flights last week because major carriers have not invested enough to overhaul reservations systems based on technology dating to the 1960s, airline industry and technology experts have said.

Airlines have spent heavily to introduce new features such as automated check-in kiosks, real-time luggage tracking and slick mobile apps. But they have avoided the steep cost of rebuilding their reservations systems from the ground up, former airline executives said.

Scott Nason, former chief information officer at American Airlines Group Inc., said long-term investments in computer technology were a tough sell when he worked there.