A double-deck aircraft has two decks for passengers; the second deck may be only a partial deck, and may be above or below the main deck. Most commercial aircraft have one passenger deck and one cargo deck for luggage and ULD containers, but only a few have two decks for passengers, typically above a third deck for cargo.
The first full double-deck aircraft was the French Breguet Deux-Ponts. The first partial double-deck jet airliner was the widebodyBoeing 747, with the top deck smaller than the main deck. Boeing originally designed the distinctive 747 bubble top with air cargo usage in mind. The small top deck permitted the cockpit and a few passengers and nose doors with unobstructed access to the full length of the hold. Most 747s are passenger jets, and a small percentage are cargo jets with nose doors.
The first full double-deck jet airliner is the Airbus A380, which has two passenger decks extending the full length of the fuselage, as well as a full-length lower third deck for cargo. Singapore Airlines took delivery of the first A380-800 in a ceremony in Toulouse, France. SIA had fitted them with 12 private luxury suites and two double beds. The A380 can hold up to 500 passengers and 25 crew.