What occurs in straight-and-level flight when thrust exceeds drag?

In straight-and-level flight, when thrust exceeds drag, the aircraft will experience an increase in speed. This is because thrust is the force that propels the airplane forward, while drag is the aerodynamic resistance that opposes that forward motion. When thrust is greater than drag, the net force acting on the airplane is positive, resulting in acceleration.

In straight-and-level flight, the balance of forces is crucial; overall, the lift force must counteract the weight, and thrust must counteract drag. If thrust increases beyond drag without a corresponding increase in weight or decrease in lift, the excess thrust translates directly into an increase in the aircraft's forward speed.

The other scenarios are not applicable in this context. For example, altitude would remain constant since we are considering straight-and-level flight, and changes in lift and weight don’t occur solely based on thrust and drag considerations in this scenario.