I would be willing to bet an economic externality such as the cost and availability of Starfighters and crews. Especially for what appears to be a US based company.
As I recall, it's not only a US company but it was founded by a former Air Force F-104 pilot who passed away a couple of years ago. They fly those planes because it's what they are really good at.
The Air Force and NASA used the planes for high-altitude test missions, and so there is some comfort in outsourcing those missions to the company. I've always been under the impression that most of their business was government stuff, but I could be all wrong about that.
A MiG 29 is still on the trailing edge of what's considered state of the art for fighter aircraft. It's essentially Russia's version of the F-16/ F-18. I would imagine that mid-century F-104's would be much more affordable.
The Air Force and NASA used the planes for high-altitude test missions, and so there is some comfort in outsourcing those missions to the company. I've always been under the impression that most of their business was government stuff, but I could be all wrong about that.