16 4.5" AA guns (8x2)
48 2pdr AA (6x8)
45 aircraft  

Originally intended as the fourth ship of the Illustrious class, Indomitable was altered while building to accommodate more aircraft at the price of 3in less armour on the hangar sides. The flight deck had effective dimensions of 680ft x 95ft, later lengthened to 745ft, and it was raised by 14ft to accommodate a second hangar. The catapult could launch 14.000lb at 66kts. The new upper hangar measured 458ft x 62ft x 14ft, and the after part of the original hangar was retained as the lower hangar with dimensions of 168ft x 62ft x 16 ft. The forward lift was increased to 45ft x 33ft, the after one remained 45ft x 22ft, and both could take 14.000lb. Petrol stowage was 75.110gal and it was found possible to operate 56 aircraft. The 3in armoured flight deck was retained but there were some alterations in the decks outside this area, the lower gallery decks being 2½in-2in over the magazines, and the lower or upper hangar deck 1½in over the machinery spaces.

Modifications;
HMS Indomitable had only 24 2pdr (3x8) when completed, and did not mount her full outfit until April 1942. In April 1944 she had 12 40mm Bofors (2x4,2x2) added and at the end of the war she also had 13 single 40 mm Bofors and 36 single 20 mm Oerlikons.