It depends I suppose. In my case I only just got to journeyman which is supposed to trigger the achievement at 500…but didn’t trigger until 600…so…you may need to fly another couple of hundred miles to be done… 
It depends I suppose. In my case I only just got to journeyman which is supposed to trigger the achievement at 500…but didn’t trigger until 600…so…you may need to fly another couple of hundred miles to be done…