As a student pilot in the US you can fly without a passenger but also with other restrictions like your flight instructor has to give you an endorsement to fly and most won't give you an unrestricted endorsement. It is really there to get you a certificate and not as a way to bypass it. All other require a certificate (technically it is not a license but rather a pilot certificate). https://en.wikipedia.org/wiki/Pilot_certification_in_the_Uni...