§ 509-h. Operation by person not licensed to drive a bus. The motor carrier shall not knowingly permit any person to operate a bus carrying passengers unless the driver meets all of the requirements of this article; except that a motor carrier may permit a conditional school bus driver who is not otherwise disqualified under the provisions of this article to operate a bus for a period not to exceed ninety days or a longer period if granted a written extension of such ninety day period by the department pursuant to regulations established by the commissioner. Such regulation shall authorize extension for at least that period of time necessary to review information regarding the prior criminal history of the applicant.