At one time using a computer system required training.  Not everyone will remember what older mainframe/terminal systems were like but user-hostile doesn’t completely convey the response. Here’s an example of how to add a frequent flyer number to your itinerary, from the old character-based Sabre airline booking system from American Airlines (and others): Using the abbreviated entry, add the FQTV (code for a frequent flyer number) number NW 759964796 to the PNR for the second…