I occasionally replace bourbon with a quality amber rum and some have called it a Paper Boat. Looking up Paper Boat there seem to be several variations.
I've heard of others doing the same and will add this version to Difford's Guide. I've also seen a Paper Boat made into a long drink, but that seems too much of a stretch from the Paper Plane.
Bourbon, Campari, Aperol, and lemon juice make a fine Paper Plane! Some folks on the west coast are replacing the lemon with lime, calling it Ruby Sippers.
Made this tonight with Amaro Nonino which I purchased today just to make this and used Aperol as suggested. I found it a bit tart so next time will try with 1/2 oz. lemon (or maybe 3/4 oz. Myer lemon?) and report back.
Another iteration here, as I switched Aperol for Aperitivo Nonino. This decreases the bitterness slightly, but adds more layers of flavor as I find Aperitivo Nonino more complex than Aperol. This version benefits from a less assertive bourbon, though, to let the Aperitivo come through. I went with Wild Turkey Longbranch today.
I ran out of Aperol, and because substituting Campari makes it quite tart I added a dash of Benedictine. Wow, that made it better than the original. It brings in the sweetness while also adding even more herbal intrigue than the Nonino alone.