.AERO TLDs are restricted to members of the aviation community such as airlines, airports, and qualifying companies and individuals. When you place an order for a .AERO domain, you need to submit an ENS (Eligibility and Name Selection) ID and password to prove your eligibility.
To obtain an ENS ID, go to the .AERO registry page https://www.information.aero/node/add/request-aero-id and complete the application form. You may be asked to provide supporting documentation such as an Airline Operating Certificate or a pilot's license. If your application is approved, the registry will send you your ENS ID and ENS password, usually within a couple of days. You can then complete the domain order form.
For more information, see https://www.information.aero/registration/faq