We’ve discussed internally and decided to no longer allow requests for airline callsigns without an existing livery in the app itself. There are likely hundreds, if not thousands, of callsigns we can dig up. This is not a great use of resources for a small team or precious votes.
The best way to see your desired callsign in-app is to support the feature request for the livery itself. Other requests similar to this will be closed as discovered over time. Thanks!