Here I have seem to have found a little viewed YouTube video where someone gets their phantom and claims to fly to 1000ft.
At around 2:50-3:00 he seems to be the highest. This was filmed as it says in the description Saginaw Michigan. He could have very well been in the way of any helicopters or low flying aircraft. I’m not sure if this person was not aware of the 400ft thing or not. This same exact person has done the same thing with a phantom 3.
I hate beating people up for this but someone needs to break the news to him and other people who range test drones. It’s just unsafe.