Is divided into three parts.
The hangar deck has enormous blast doors dividing the deck into three separate sections. This protects the hangar deck and stores located inside from damage during battle. Originally there were three aircraft elevators to move the planes to and form the flight deck from the hangar deck. Later modifications removed one of the elevators.
It's a very large space, crammed with interesting exhibits, history and many artifacts of the Yorktown, and a special exhibit about her sister carrier the USS Franklin and how it survived crippling damage from an air attack in March 1945 due to the heroism and effort of her crew. The attack had killed 800 of its crew, yet the ship was saved and returned to service after incredible damage.
A 40mm gun mount from the Franklin is on display on the hangar deck, with some damage from the attack still visible.
There's also a very good movie shown in by the memorial about the Franklin to the left of the gun mount that is well worth watching.
There's plenty of aircraft on display as well:
A Stearman biplane navy training aircraft:
The many types of aircraft that the Yorktown operated are on display:
The F4F Wildcat -
The initial main American naval fighter of the war. While inferior to the Zero, it was made famous in the hands of aces like O'Hare and Thatch, and proved to be able to meet the Zero on its own terms when the right tactics were used.
The F6F Hellcat - The US Navy's highest scoring aircraft of World War 2 and successor to the Wildcat:
The F4U Corsair:
The Douglas A-1 Skyraider
The Grumman Avenger TBM torpedo bomber:
The SBD Dauntless dive bomber:
The F9F Cougar - bringing the Yorktown into the jet age. Subsequent Navy jets quickly began to become too heavy to operate off the Yorktown.
Yorktown recovered the astronauts of Apollo 8, after their historic flight around the Moon in December 1968; so there are some space related exhibits, including a mock Apollo capsule:
And a mock up of the Friendship 7, the Mercury spacecraft piloted by John Glenn.
The hangar deck makes for an impressive display of the history of American naval air power.