Final answer:
The airplane will gain altitude at a steady rate by applying thrust from its engines and generating lift with its wings.
Step-by-step explanation:
The airplane will gain altitude at a steady rate by applying thrust. Thrust is the force generated by the airplane's engines that propels the aircraft forward and allows it to overcome drag. As the airplane moves forward, the wings generate lift by creating a pressure difference between the upper and lower surfaces of the wings, which enables the airplane to gain altitude.
For example, during takeoff, the engines produce high thrust, and the wings generate sufficient lift to lift the airplane off the ground. As the airplane continues to climb, the pilot adjusts the thrust and the flight controls to maintain a steady ascent rate.