Physics is physics, so citizen aircraft don't look all that different from human ones in the major ways - wings, jet engines, tails, rotors, and the like. Differences tend to be more from points of doctrine than anything else. For example, most of their aircraft are designed for short rough field performance or as flying boats to facilitate operation from small islands or boats. Believe it or not, the old 1950s "Sea Dart" interceptor is a fairly good match to their most common fighter, though the wings are extended, with canards, so for those fans of classic warbirds - think a dart with the wing to cockpit root extensions of a F-18 Hornet and the canard whiskers of a IAI Kifir C-7.
But I'm not really here to talk about fighters - chances are you won't see them up close. Citizen choppers, are pretty common on the other hand.
One running theme you'll see in most of these designs, is a resemblance to flatfish, rays, perhaps airplanes that have been stepped on and had the wings removed. Partly its the different weapons used, and what they feel is safe. In human attack helicopters, the design is often pilot in back, gunner in front to keep the design as narrow as possible, thus presenting a smaller target when facing the target head on. Citizens prefer side by side seating, either just two people together, or a pilot in the middle and gunners on either side. This presents two advantages. First - each crew member has only a specific sector to watch, rather than the entire field. Secondly, the wide body shields the top mounted engines and a large section of the rotor disk from laser fire, as well as masking the exhaust from infrared missiles.
Most commonly seen is the flounder shaped utility helicopter - one of the three person models. It seems to have a cargo bay, complete with which underneath it, but no one has observed it carrying passengers. Its comparable in size to a late model UH-1, but the coaxial five-blade rotors and proportionately larger engines give it a much greater under-slung cargo capacity, and fiarly impressive speed for something in its class.
Furthering the comparison to the UH-1, there is an armed version of this copter as well. Fortunately, there are some clear differences that allow an observer to tell the two apart - but it is highly advised to find cover first, and then confirm the model! Each of the two side crew have a rotating laser turret beneath them, and
the fuselage is notably pinched behind the cockpit, giving them a degree of view to the rear - about 340 to 350 degrees of the machine can be covered, with only directly behind being safe. The long internal cargo bay is divided into three bomb-bays, each carrying missiles or actual bombs - estimated to be in the fifty to one-hundred kilogram range. (Interestingly, unlike the common human practice - citizen helicopters almost never use unguided rocket pods.) Increased drag from the turrets, as well as the weight of armor, batteries, and munitions make this version notably slower.
One of the weirder machines to accompany the aliens is their high speed transport craft. Its a strange amalgamation of helicopter, swing wing jet, manta ray, and another abortive aviation project - the AH-56 Cheyenne. It has a pusher ducted fan, pop-out wings, and a single six blade rotor. (Anti-torque seems to be more ducted jets in the tail, rather than a side rotor.) Apparently the craft takes off vertically, with the wings retracted out of the rotor down-wash, but once it accelerates, the wings pop out to provide some or most of the lift, unloading the rotor hub and allowing it to provide mostly thrust. Actual capacity seems to be quite limited to just soldiers, since all that equipment engines take up space and have weight of their own. On the other hand, it has both for and aft laser turrets, and is quite effective at what its designed for - dashing into enemy territory to deliver a commando team, or dashing out with rescued personnel.
Of course there are more sundry transports of various sizes, and a second type of attack helicopter, but the former are not often seen outside Citizen territory, while the later seems to be a newly designed machine with little information available, so this report will have to suffice for now.