Question

When a jet plane is cruising at high altitude, the flight attendants have more of a "hill" to climb as they walk forward along the aisle than when the plane is cruising at a lower altitude. why does the pilot have to fly with a greater "angle of attack" at high altitude than at low?

Answer 1

Probably because the Bernoulli effect (lift) is insufficient in thinner air to keep the plane aloft - increasing the angle of attack will increase the lift on the airplane