What term describes the maximum altitude at which an aircraft can maintain level flight?

The term that accurately describes the maximum altitude at which an aircraft can maintain level flight is known as the absolute ceiling. At this altitude, an aircraft can no longer sustain level flight and any further increase in altitude would result in a descent. This is largely due to the decrease in air density at higher altitudes, which affects lift and engine performance.

The absolute ceiling is an important consideration for pilots, as it represents a critical limit for operational flight characteristics. It is distinct from the service ceiling, which refers to a slightly lower altitude where an aircraft can still maintain a rate of climb (however minimal) for a specified period of time. Understanding the absolute ceiling helps pilots ensure safe operations and avoid situations where they might inadvertently exceed the aircraft's performance limits.