.aero
Top-level domain
.aero is a sponsored top-level domain used in the Domain Name System of the Internet. It is the first sponsored top-level domain based on a single industrial theme. The aero domain is reserved for companies, organizations, associations, government... Wikipedia
Actual use: Players in this industry seem to be using it, further usage just like.com,.info and other TLDs
Intended use: Airlines, airports, and other parts of the air-travel industry
Registration restrictions: Credentials of applicants are checked before registration is permitted, but then any domain can be registered