GDS Access?
 

I seem to remember that a few years back I was able through Flyer Talk to pay for access to worldwide GDS through a couple of suppliers.
you could see inventory availability in bucket classes including frequent flyer seats, but could not actually book.
Are these still around? It’s an age thing that makes me forget. :)

I don't even know what GDS is. It sounds like these have been links provided by users

GDS is Global Distribution System used by the travel industry to book airline tickets.

I’ve found what I was looking for

https://www.expertflyer.com/