Most PBF group members are volunteer pilots, thus many PBFs are also called Volunteer Pilot Organizations (VPOs). The ACA website's Directory of Groups is the only place where all such groups as are known are listed for the benefit of patients, social workers, medical referral groups, agencies needing assistance, or the volunteer pilots who wish to find all groups they might want to join. In addition the website features an online automated referral system that, using a form filled out by someone making inquiry, will provide a list of appropriate groups serving the states where a flight is needed. Then with one click the information in the form can be sent to each organization the person wishes to be contacted.