I have to disagree with you on the airline pilots bit - these are professional air crews that are used to seeing things in their field of vision at whatever altitude and reacting accordingly - if we decide to rubbish their opinion and abilities who do we believe? These are trained professionals with no hidden agenda - if they see something, they report it, without bias - show me one forum/facebook group populated by drone operators that can say the same. I know several people who have flown drones to the heights mentioned in some of these reports - they aren't 'commercial/consumer' kit, they are custom built stuff that can perform way outside the operating window of DJI phantoms - they have used them, legally to track/film model rocket launches and weather observations - if they can build gear capable of this, then so can other people - just because you haven't seen this type of kit doesn't mean it doesn't exist 
