CMAP remains voluntary in a formal sense. Crew members must affirmatively consent before their airlines add them to the program, and those who decline may use regular passenger screening to reach the sterile area. For crew members, the practical choice is between consenting to facial comparison or losing access to the separate expedited lane that KCM provided. A failed biometric match or a random selection for additional screening sends the crewmember to a passenger checkpoint. The program relies on data that airlines already provide TSA through Master Crew Lists for international operators and Master Personnel Lists for domestic only operators. The practical effect is to bring an industry facilitated crew credential program into the government’s biometric identity verification infrastructure.