zlacker

Consider the vectors of the four forces (thrust, drag, lift, weight). The thrust only needs to equal the drag at a given airspeed, not the weight of the vehicle. (Unless it's climbing vertically.) The weight is countered by the lift generated by the wings, which, given the efficiency of airfoils, is very more or less why it all works: they produce a positive lift-to-drag ratio.

Put another way, weight pulls it down, thrust moves it forward, the resultant lift keeps it up, and drag limits its speed. Only rocketeers and fighter/aerobatic pilots need to really worry about the thrust to weight ratio as a constraining factor, because the vertical flight regime matters to them. From your average bugsmasher to your commercial airliner, it's not a factor (to the disappointment of pilots everywhere).

Consider that a Cessna 172 has a glide ratio of about 9:1, so it can go 9 units forward for every 9 of altitude it gives up. If that's hard to intuitively grasp, consider that it's traveling through a fluid. Surfing, even. The interaction with that fluid is why it works.

That any more satisfying?

>>handed+(OP)
So the 'glide ratio' is essentially a multiplier from 'thrust' to 'lift'?

>>rocqua+H
Sorry, I was unclear. That glide ratio is unpowered (and approximate). Any thrust will only increase that ratio.