(5) When a Public Inquiry has been ordered the Attorney General may cause a notice, to be called a notice of inquiry, to be served upon the owner, operator, hirer and person in command of any aircraft involved in the accident, as well as upon any person who in his opinion ought to be served with such notice. The notice shall contain a statement of the questions which on the information then in the possession of the Attorney General he intends to raise on the hearing of the inquiry, and the Attorney General may, at any time before the hearing of the inquiry, by a subsequent notice amend, add to, or omit any of the questions specified in the notice of inquiry.