1) every airplane has mass and gravity force attracts it to the Air;
2) in order to hang in the air, this force must be eliminated by the same magnitude, but opposite direction force. In airplane this force is generated by wings (Lift force);
3) in order for wings to generate Lift force, it needs to be blown over with high speed air. How to get high speed air? Just move with high speed relative to the air. E.g. move quickly forward.
4) when airplane moves with high speed it generates not only Lift force from the wings, but traction on airplane surface generates Drag force. Because of this force airplane must constantly battle with it and use engine power to maintain forward speed.
That is it. There is no wishing or undefined part in equation why plane flies. So whenever plane has enough forward speed and appropriate to its weight wings, it will fly. Did you know - there practically can not be such big force applied to wing during the flight that could break wings off.
Why? Wings are made to be elastic and move a bit during turbulence, and they are constructed so, that they can hold more than double theoretical forces encountered by wing during the flight. This calculated force is always applied during wing testing before manufacturing any plane (wings are literally bend from the tips till they break).
There is simple experiment to feel that Lift force by yourself. While driving in car, just (CAREFULLY) extend your arm through window, palm facing downwards. Then just slightly rise front part of palm. You will feel Lift force, that is the same as Lift force generated by wings. Just they has much much much bigger area, so they generate much much much more Lift force, that can even lift whole airplane.
So for every airplane critical is air speed (not ground speed, as airplane during flight "sits" on air, and not ground, so wind speed is what it needs). By the way, because of that, every airplane takes-off and lands against the wind - so even ant 0 ground speed, the air speed is already more than 0, and wings are already generating small amount of Lift.
Now you know, why airplane "hangs in the air". In my next posts I will be writing how exactly wings generate Lift force and how jet engines work.