these are the official reasons, of course. The real reason aircraft fly is of course....
...PFIL, or Passenger Fear Induced Lift. The lift comes from all the pax grabbing onto their armrests and pulling. It is easy to see. The engines and take off roll are simply there to put enough fear into the pax. On takeoff, as the noise and vibration picks up, they all grab hold of their armrests and off you go.
On approach, since they're all relaxed after inflight meals and a drink or two, you need flaps and perhaps even spoilers to make sure you get enough lift. If you find yourself below the glideslope, you might even have to add a burst of power to frighten them enough!
Yes, cargo ops is dangerous. It really takes quite a pilot to scare a cabin full of mail!
I thought I was doing good trying to avoid those airport hotels... and look at me now.