What signifies the completion of aviation security screening?

The issuance of a boarding pass acts as a key indicator that the aviation security screening process has been completed successfully. When passengers go through screening, their identification and travel documents are verified, and they undergo security checks that include metal detectors, x-ray machines for luggage, and sometimes additional screening measures. Once this entire process is finished, and a boarding pass is issued, it confirms that the passenger has met all necessary security criteria to access the aircraft.

This step is critical because it not only allows the airline to ensure that all security protocols have been followed, but it also serves as an official document for the passenger, granting them the ability to board the aircraft. The other options, while relevant to the security process, do not signify completion in the same direct manner. For instance, the collection of luggage is part of overall operations but does not mark the end of screening as it relates to the passenger's security check. Scanning boarding passes and confirming identity are important components during the screening but occur as part of the process rather than signaling its completion.