After partially playing through a campaign with the aircraft feature enabled, I must say that they are a welcome addition to the game that I intend on playing with more in the future. Despite this, I feel as though aircraft, their basing and design need some tweaks in order to make them usable in line with other vehicles in the game.
The first and most pressing issue is the prodigious amount of ammunition that aircraft, even ultralights, use in the course of their attack runs. One of my aircraft is an ultralight with a 1000kg bombload, and two wings of thirty ultralights each use enough ammo for an entire front with multiple infantry or light tank brigades. The industrial points and metal required to sustain even a small air bomber wing is more than enough to create entire battalions of light tanks each turn. The resource and ammo usage becomes even more difficult to contend with when using even light aircraft, let alone medium or heavy bombers. I understand that aircraft are very, very powerful when used properly and must be balanced, but the prodigious ammo consumption of said vehicles is beyond what I think is rational or enjoyable in the course of a war in shadow empires. How this ammunition usage problem would be remedied while maintaining balance is not entirely known to me.
The secondary issue stems from aircraft design and its impact on overall model design time. I understand that there is an aircraft research council that also assists in research, but it is rather ambiguous to the player as to whether or not said council actually discovers models for aircraft, or if they just research new technologies. Because of this ambiguity, it can make the player seem as though activating aircraft for a new game will just drastically increase the time for discovering any desired weapon model, such as an assault gun or heavy tank. I think it would be better for design clarity and speed if the aircraft research council clearly discovered aircraft models concurrently with the model design council.
The third and most minor issue comes from dealing with airbase sizes. Simply put, the nature of airbase limitations make it prohibitively expensive to field larger and larger aircraft, especially when airbase level is tied to the maximum level of the city the airbase zone is being constructed in. I am not sure of how to solve this issue completely, as there should be limitations on aircraft due to their size. A heavy or medium aircraft should not be able to use an airbase fit for ultralights, but the system still seems a bit restrained. I think that light aircraft should also be able to use level 1 airbases, or the maximum airbase level should not be tied to the level of the city in the zone in which the airbase is being built. Another solution would be to add another feature to the aircraft design system, that of landing gear. If an aircraft features a more rugged landing gear system, it would be able to use an airbase that's one level lower than the usual airbase level for that airframe. For instance, a medium aircraft with a rugged landing gear system would be able to use a level 2 airbase instead of a level 3 one, but it would also be saddled with a weight penalty.
Overall, I enjoy aircraft more than I dislike them, but I just wanted to share my thoughts on the matter somewhat.