Getting a 2nd aircraft is absolutely essential for the early-mid game, and at the moment there are only two ways to do it: build one (slow, expensive) or steal one (fast, free).
Stealing is just way more effective, particularly since it lets you get a Helios instead of a Manticore. But it feels kind of evil, not to mention abusive.
It would be nice if you could get faction aircraft without having to kill their owners. Possibilities could include:
a) Factions offering aircraft as one-off rewards for difficult missions. Similar to what they do now, except that you get paid in aircraft instead of in raw resources.
b) Rescue missions where the faction gives you the location of a crashed aircraft – you have to travel there, secure the location, repair the aircraft, then fly it back home.
c) Just allowing Phoenix Project to buy aircraft from factions once you reach Supportive (25-49) status with them.
d) Missions from factions where the reward is that they'll build you something with their tech. So you could choose between an aircraft or various combinations of weapons/armour/vehicles. However, you wouldn't get it straight away - there'd be a time delay (representing them manufacturing it for you).