Armoured carriers and aircraft capacity. When talking about the British armored carriers, it is often said that the protection was bought at the expense of aircraft capacity.
This is only half true.
The British Illustrious class aircraft carriers entered service in the years between the Yorktown and Essex class aircraft carriers. For this reason, the Illustrious class are often compared to them.
Compared to the Yorktown class, the Illustrious class was slightly larger, having a design displacement of 23,000 tons vs 20,000 tons for the American carrier. However, the Yorktown class carried over 80 aircraft in service while the Illustrious class carried about 40 aircraft.
Even HMS Indomitable, a modification of the Illustrious class with a larger double stacked hangar (designed specifically to carry more aircraft), typically carried 48 aircraft in service.
A very large difference between the British and American carriers.
Typically it is said that this difference In aircraft capacity is due to the armored design of the British carrier. However, while the design of the Illustrious class did limit the size of the hangar, it was not that much of a difference.
Compared to the Yorktown class, the Illustrious class had a hangar that was slightly over 80% the size of the American carrier. The double hangar Indomitable actually had more space for aircraft than the Yorktown class.
So why the huge difference in aircraft capacity?
The difference in capacity comes down to American carriers having a full time deck park. A deck park is the system of storing aircraft on the flightdeck and outside of the hangar.
The United States, in its quest to maximize the offensive capability of its carriers, carried more aircraft by carrying extra planes on the flight deck in addition to the normal complement inside the hangar.
Depending on the aircraft, carrier class, and ratio of aircraft types, the US Carriers carried as much as 25% to 35% of their aircraft on the flightdeck in a deck park.
It is less to do with the hangar capacity and more to do with the fact that the US Navy used its flightdeck for aircraft storage while the Royal Navy did not.
It's also worth pointing out that the Royal Navy did eventually adopt a similar deck park to increase the aircraft complement aboard its carriers (especially once they began to operate in the Pacific).
When utilizing a full time deck park, the Illustrious class saw their aircraft complement increase to 57 aircraft. HMS Indomitable remained at around 55 aircraft (no info on whether she received a deck park) while the Implacable class, based on Indomitable, rose to a capacity of just over 80 aircraft at the end of WW2, matching the Yorktown class.
Factoring in the deck park, the British armored carriers were not that far behind the US Carriers in aircraft capacity.
*Note* The Essex class also used a full time deck park, allowing them to carry up to 110 aircraft. This, coupled with the fact that they were designed to an even larger 30,000 ton design, means that their capacity was vastly higher than the earlier British carriers. Hardly a fair comparison though it is often used when discussing the various carriers.