In order to facilitate the making of investigations by the commission in the interest of public safety and promotion of aeronautics, the public interest requires, and it is therefor provided, that the reports of investigations or hearings or any part thereof, shall not be admitted in evidence or used for any purpose in any suit, action or proceeding growing out of any matter referred to in said investigation, hearing or report thereof, except in case of any suit, action or proceeding, civil or criminal, instituted by or in behalf of the commission or in the name of the state under the provisions of this chapter or other laws of the state relating to aeronautics. No member of the commission, or the director, or any officer or employee of the commission shall be required to testify to any facts ascertained in, or information gained by reason of, his official capacity, or be required to testify as an expert witness in any suit, action or proceeding involving any aircraft. Subject to the foregoing provisions, the commission may in its discretion make available to appropriate federal, state and municipal agencies information and material developed in the course of its investigations and hearings.