The first time I traveled for work with my employer I saw that I could register frequent-flyer account numbers with them and they would do the right thing there. I didn't yet have a frequent-flyer account on the carrier we usually use, but I figured I could come back and add that later.
I downloaded the airline's app, used the confirmation number for the flight as an entry point, and created an account with them. The app did all the right things for that trip.
I recently booked another trip and noticed that I hadn't yet entered the frequent-flyer account number in my travel profile (and so the app couldn't find it for me). Ok, I figured -- I'll just ask the app for my account number so I can add it to the profile. (Meanwhile, I had to use an actual phone to talk to an actual human being to connect this flight to my account.)
Nope, no way to get the account number in the app -- I'm signed in, but I apparently don't need to know the account number so they're not going to trouble me with a line in "settings" or some such.
I searched my email and found the "welcome to (us)" notice, but it didn't contain the account number either.
So I went to the web site, at which point I had to log in. After failing with my standard password algorithm I went down the "forgot password" path, which is when I discovered that my algorithm wouldn't work with them (see rant below), hence the failed login. So I reset my password with their insecure rules, logged in on the web site, and therein found my account number, which I then added to my corporate travel profile. I suspect I'll need this password at most one more time (if the app challenges me for it because it changed, which it hasn't yet).
All of this could have been averted if either the app or the welcome email had a way to find the account number. Sheesh.
In theory, now, everything should be wired up: next time I need to book corporate travel on this airline the flights will automatically show up in the app and I'll never need to directly interact with the airline. That wiring makes things easy, but it was way harder than it should have been to get the information in order to effect that wiring.
Rant: In these modern times, why in the world does anybody have password rules that do not permit any low-order ASCII character? No punctuation except periods and underscores? What is this nonsense?