Where is the point of no return?

Probably safe to say mid-point. When it's as far to go back to your start point as to go on to your end point.

I would point out that the "no return" part does not imply the mid-point. It is the point when it is no longer possible to return to your starting point safely. If I am flying 150 miles away and have enough fuel to travel 200 miles (and some reserve for safety) then the point of no return is 100 miles out, not 75 miles. It is the point when I can no longer return to my starting point safely and must continue on to the end point.