A common classification for unmanned aircraft systems is:

Gross Takeoff Weight is a crucial classification for unmanned aircraft systems (UAS) because it determines various operational capabilities and regulatory requirements for the aircraft. UAS are often categorized into weight classes, which can influence factors such as airspace usage, pilot certification requirements, and operational limitations. For instance, different weight thresholds may dictate whether a UAS must be registered or if specific airspace regulations apply, making it an essential consideration for operators and regulators alike.

Although other factors like flight range and battery capacity are relevant to the performance characteristics of a UAS, they do not serve as primary methods for classification. Altimeter type is more technical in nature and relates to specific instruments used to measure altitude rather than the overall classification of the aircraft itself. Therefore, Gross Takeoff Weight remains the most significant and standardized criterion for classifying unmanned aircraft systems.