The use of optical sensors for navigation on aircraft has receive much attention recently. Optical sensors provide a wealth of information about the environment and are standard payloads for many unmanned aerial vehicles (UAVs). Simultaneous localization and mapping (SLAM) algorithms using optical sensors have become computationally feasible in real time in the last ten years. However, implementations of visual SLAM navigation systems on aerial vehicles are still new and consequently are often limited to restrictive environments or idealized conditions. One example of a flight condition which can dramatically affect navigation performance is altitude. This paper seeks to examine the performance of monocular extended Kalman filter based SLAM (EKF-SLAM) navigation over a large altitude change. Simulation data is collected which illustrates the behavior of the navigation system over the altitude range. Navigation and control system parameters values are specified which improve vehicle performance across the flight conditions. Additionally, a detailed presentation of the monocular EKF-SLAM navigation system is given. Flight test results are presented on a quadrotor.