Originally Posted by vinnyc

As far as I could notice, you cannot do it on the AF app. You need to access your reservation the website via a browser.

You scroll down to your name section where you input personal information. Under the Travel Documents section, below your passport section, you can add your Known Traveler Number.

If your mom has TSA Pre or Global Entry or NEXUS, the PassID Number will give her TSA Pre privileges, assuming that it is a flight departing the U.S. at an airport where TSA Pre is available (most U.S. airports are, including the ones where AF flies to).

The KTN will have no use for you on the return flight back to the U.S.