No need to track 50,000 aircraft. Instead, have the stream automatically switch on when the plane is in distress, when it's losing altitude, when an emergency has been triggered, or when it's going off the flight path.
Define: 'going off the flight path'...
In theory this is a simple problem to solve, just install a couple of webcams and hook them up to the in-flight wi-fi. In some cases that might even work. But if you want it to work in all the cases, especially those cases where things are going wrong then you'll need to think this through very carefully or it will be worse than useless.
A camera is pretty trivially disabled or obstructed in the event of foul play; the exception to the rule of communications and black box data being enough to establish what the pilots were trying to do.