Upvote:2
ITA allows you to specify the list of airlines to consider, like Destination airport: IAD :: UA,AA,DL
There is - as far as I know - no way to specify βFly Americanβ directly, but once you collect the airlines codes in a string, you can save this string in a text file and reuse it every time.
See for example https://www.travelcodex.com/advanced-routing-language-in-ita/ for an explanation with examples.