One-Stop Pilot Program Act of 2021 This bill authorizes the Transportation Security Administration (TSA) to conduct a pilot program at not more than six foreign last point of departure airports to permit passengers and their accessible property to bypass domestic security rescreening at a connecting airport in the United States. Screening may be bypassed if (1) the country of departure has an aviation screening agreement with the United States setting standards and protocols comparable to those in the United States; (2) passengers cannot access their checked baggage until arriving at their final destination; and (3) upon arrival in the United States, passengers do not come into contact with other arriving international passengers (or their property) or persons who have not been screened. The TSA must ensure there is no reduction in the level of security or specific aviation security standards and requirements for screening passengers and their property prior to boarding an international flight bound for the United States, including standards or requirements regarding (1) high risk passengers; and (2) weapons, explosives, and incendiaries. If the TSA determines that the foreign countries participating in the screening agreements have not maintained and implemented comparable standards and protocols to those in the United States, it must ensure that passengers and their property arriving from the foreign airports are rescreened in the United States before they are permitted into sterile areas of the airports. The pilot program shall terminate six years after the enactment of the bill.