The list being classified as secret is distinct from a listing of an individual. There are ways that people have found out they were aviation blacklisted by the USG despite not having found that out by trying to check-in/board a covered flight.

Lots more blacklisted people could be plaintiffs, but of the people who know they are blacklisted (despite having no criminal activity) not all are interested in pursuing litigation against the USG for having been blacklisted; nor do all those harmed (even by being denied boarding) have the means to pursue the matter (or to get others to pursue it) in court.