The department, any member, the director, or any officer or employee of the department designated by it may hold investigations, inquiries, and hearings concerning matters covered by this part and the rules and orders of the department, and concerning accidents in aeronautics within this state. Hearings shall be open to the public and, except as provided in Section 21691, shall be held upon such call or notice as the department deems advisable. Each member of the department, the director, and every officer or employee of the department designated by it to hold any inquiry, investigation, or hearing may administer oaths and affirmations, certify to all official acts, issue subpoenas, and order the attendance and testimony of witnesses and the production of papers, books, and documents. If any person fails to comply with any subpoenas or order issued under the authority of this section, the department or its authorized representative may invoke the aid of any court of general jurisdiction. The court may order such person to comply with the requirements of the subpoena or order to give evidence touching the matter in question. Failure to obey the order of the court may be punished by the court as contempt.