The original SABRE dates back to the 1950s, and was not an airline-customer-facing system; SABRE dates to an era when the phone interface was used by airline ticket agents.
So if you're going to argue that the design is wrong, you need to argue for why it was wrong for the 1950s use case and interaction patterns, not try to retrofit 2014's use cases and interaction patterns onto it.
Now, yes.
The original SABRE dates back to the 1950s, and was not an airline-customer-facing system; SABRE dates to an era when the phone interface was used by airline ticket agents.
So if you're going to argue that the design is wrong, you need to argue for why it was wrong for the 1950s use case and interaction patterns, not try to retrofit 2014's use cases and interaction patterns onto it.