What is the biggest military aircraft?
Because the AN-225 is not a military aircraft and Zeppelin will be winner, there is no one biggest plane.


C5 Galaxy = 76 meters long, 68 m wingspan, 20 m high, wing area:576 m2
An-124 = 69 meters long, 73 m wingspan, 21 m high, wing area: 628 m2   
(Bonus:) Hughes H-4 Hercules (Spruce Goose on picture) = 66.55 meters long, 97,54 wingspan, 24 m high, wing area: 1 061,8 m2


See this : 

Source:https://fr.m.wikipedia.org/wiki/Hughes_H-4_Hercules#/media/Fichier%3AGiant_planes_comparison.svg