Which of the following is a vital document that must be presented when applying for an ADP?

A valid driver's license is a vital document required when applying for an Airside Driving Permit (ADP) because it serves as proof of the applicant’s eligibility and competence to operate a vehicle legally. The ADP is specifically designed for individuals who will be driving within the airfield areas, which demands a level of expertise and understanding of regulations associated with airside operations. A valid driver's license confirms that the individual has undergone necessary training and assessment to operate a vehicle safely, meeting local or national driving regulations.

In contrast, while a birth certificate, medical report, and letter of recommendation may serve specific purposes in various applications, they do not validate an individual’s driving capabilities or authorize them to operate a vehicle in a regulated airside environment. Therefore, having a valid driver's license is foundational for the ADP application process, ensuring that all drivers meet the legal requirements for driving on airport premises.