Except in dire circumstances, airplanes are not struggling to produce sufficient lift. What matters is to produce it with reasonably low drag, up to all the oth

Except in dire circumstances, airplanes are not struggling to produce sufficient lift. What matters is to produce it with reasonably low drag, up to all the other constraints that go into making a practical airplane for its intended purpose. There are some airplanes that can be in a situation of flying, but unable to climb or even maintain altitude, with flaps fully lowered. In such a situation, only carefully raising the flaps will allow it to climb away.