Not specifically what you want, but perhaps a start - UA has a page on .bomb thath has a list of destinations that is supposed to have good saver availability. Saw a ad-size thing down the right side of a page for it yesterday, but don't remember which page exactly, but I'm pretty sure it was one of the MP pages. I'll see if I can figure out which one.

I didnt click on it, so don't know if it can filter by departure city too. Also don't know how often it's updated, maybe not more than monthly - however, several years ago, UA used to email the list out based on MP settings.

if you're looking for a typical spring break destination (I.e., FL, Carribean), I wouldn't hold my breath - these are mostly probably sold out long ago, or the few remaining seats are probably waiting for UA to pick up last minute planners who are willing to pay $. Especially if you insist on non-stop, particularly Carribean which is much better served on UA from EWR and to a lesser extent, IAH.