What defines it
Level flight is not about wings being flat — it's about the forces being balanced. Lift equals weight, so altitude doesn't change. Thrust equals drag, so airspeed doesn't change. When these two pairs are balanced, the aircraft flies straight and level.
The aircraft can be in level flight at any altitude and any airspeed within its performance envelope. The pitch attitude required to maintain level flight varies with airspeed — at low speed, a higher angle of attack (nose higher) is needed to produce enough lift.
Quick reference
| Altitude | Constant |
| Airspeed | Constant |
| Heading | Constant (straight and level) |
| Lift vs Weight | Balanced — Lift = Weight |
| Thrust vs Drag | Balanced — Thrust = Drag |
"Wings level" ≠ "level flight": A banked aircraft can still maintain constant altitude in a coordinated turn, but it requires more total lift than straight and level flight — the wings must produce enough lift for both the vertical component (opposing weight) and the horizontal component (curving the path).