This category includes letters, letter packages, postcards, postal cards, and aerogrammes. All LC mail receives First-Class Mail service in the United States, is dispatched by the fastest transportation available, and travels by airmail or priority service in the destination country.
Aerogrammes are letter sheets that can be folded into the form of an envelope and sealed.
Aerogrammes are intended for personal communication and may not include enclosures. Neither tape nor stickers may be used to seal aerogrammes. This is similar to domestic parcel post.