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I recently Stumbled on this Why Planes Don't Fly Faster on youtube and it talked about how less speed is more economical for airlines and he also said something that plane above and below speed of sound will face less air drag, in the region of speed of sound maximum air drag will be experienced. I am not quite able to understand what he meant there?
Question In the first part :
1. Why planes fly at M .8?
2. Why there is less drag above and below M 1 ?.
Also in one of the comment someone said
What generates the most thrust in a turbofan is the bypass air and not the turbine. Usually the fan generates around 80% thrust and the turbine generates around 20%. There are some rare cases where the turbine generates more thrust, but in most high bypass turbofans (which are the most we use today) the fan is what generates most of the thrust.
Question Here : Why turbofans generate most of the thrust with the cold flow?
And that the video is mostly incorrect, can someone guide me here, I am sort of confused.
Lastly : Is that youtube video wrong? , I want to know this because I really liked his way of explaining , and I really want video to be right, but I am confused by the some comments, if one could guide me if video is wrong or right, it would highly appreciated?