Crew-Opt is a set-covering method that uses column-generation to produce nearly optimal solutions to crew scheduling problems. We presented this method at the previous workshops. Since that time, we have been using Crew-Opt in a number of experiments and practical trials for a wide range of situations. At this workshop, we will review the basic principles of this method and report on our work with complex public transit problems. Further development carried out at the University of Montréal (GERAD), together with the rapid increase in Computer CPU speed, opens up the possibility of solving large crew scheduling problems optimally with this approach.