Flight deck
The flight deck of an aircraft carrier is the surface from which its aircraft take off and land, essentially a miniature airfield at sea.
In early carriers, the flight deck was a sort of long flat superstructure built above the rest of the ship; this was both a relatively simple addition to make, and offered a little extra room for airplanes strugging to gain altitude after taking off. These decks were made of wood and would occasionally include a small ramp at one end to aid in take-off. Ships of this type were still being built into the late 40s, in the form of the US Navy's Essex and Ticonderoga class carriers. The earliest carriers were converted merchant ships, fleet colliers or cruisers, especially battlecruisers that otherwise would have had to have been discarded under the Washington and London Treaty.
Early carriers were vulnerable to fire on deck, particularly during refuelling. After refuelling, fuel lines in the deck would be purged with exhaust gasses to reduce the vulnerability to fire.
Later the flight deck was designed into the carrier hull, becoming a structural element, and later still, were made of steel. Aircraft are given extra speed to assist take-offs by catapults.
Another innovation was the angled flight deck, in which the aft part of the deck is widened and a separate runway positioned at an angle. This allows for simultaneous takeoffs and landings.
A more recent innovation is the "ski jump" deck, which is curved upwards at its forward end, helping aircraft clear the waves more quickly.
No matter what the design, the flight deck is a very busy place, with aircraft being brought up and taken down by elevators, moved around the deck, not to mention the takeoffs and landings. It is also a somewhat dangerous place; a bad landing can send an out-of-control plane crashing through dozens of others loaded with fuel and ordnance.
Flight deck is also cartoon by Peter Waldner.