Their website seems to stipulates the handhelds for ground use only.
Yes but they do supply a headset adapter with the radio. If you try and use it then the feedback makes it useless, whether on the ground or in the air.
I recommend looking at Vertex handhelds. They are made by Yaesu and I'm very pleased with mine.
The A6 is also fine but I only use it when on the ground at our strip