What is a key disadvantage of inertial navigation systems (INS)?

The key disadvantage of inertial navigation systems (INS) is that accuracy decreases with range. INS relies on internal sensors to calculate the position of an aircraft based on its initial position and its acceleration over time. However, over extended distances, small errors in the sensors or calculations can accumulate, leading to significant deviations from the actual position. This phenomenon is known as "drift," which becomes more pronounced the longer the system operates without external recalibration or updates.

While other factors such as cost, maintenance, and complexity may play roles in the practicality or implementation of INS, it is the degradation of accuracy over range that significantly affects the reliability of navigation in longer flights or missions. This is particularly crucial in military operations, where precise navigation can be vital for mission success and safety.