am currently in Sapporo, Japan and catching a flight early on Friday, 27 December. I am planning to either use the Airport Limousine Bus or the Rapid Airport to get to the airport. I also have a JR Rail Pass. Can I use the JR Rail Pass for the bus service?
You cannot, because the three bus companies serving CTS are Hokkaido Chuo Bus, Hokuto Kotsu, and Donan Bus. JR Hokkaido is not one of them, and apparently a JR pass will not work on non-JR transportation (note there are exceptions but none apply here).
Instead, what you may do is to use JR Hokkaido's "Express Airport" train which will take you to the airport from Sapporo station.
