I had to look into ~19 imagery firms for some telco work in Canada last year.
There are private jets that can capture 10cm imagery and can pick the ideal weather window to fly in.
There are also firms that fly balloons 20 - 80 KM off the ground that can capture 4cm imagery.
The space is pretty busy.
Maybe I'm missing something obvious, but what about drones? Probably would have to get permits most likely, but still might be cheaper than alternatives (although balloons are hard to beat when it comes to costs, not always reusable though).