In the airline world, multiple environments outside of production have been standard since 89 or 1990 as far as I know (maybe earlier, but idk). That’s before

In the airline world, multiple environments outside of production have been standard since 89 or 1990 as far as I know (maybe earlier, but idk). That’s before any airline would use internet to talk to each other, but using their own network. I think it was mostly motivated by allowing airlines to train their agents on a dedicated system but also rehearse their migration from their system to a GDS without perturbing any other airlines flights (or their own for that matter).