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Sabre Advance Notification 16279 (attached) outlines how Sabre will sunset use of 4 prefix. (Sunset date has yet to be set by Sabre but expected later in 2022). Clients are moving to this new prefix already and Faces needs to be ready to handle this. Sabre confirm that if a client of theirs has not been migrated to this new process then sending AA content with a 3 prefix will still work okay without any impact to the client.
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