Out of the box before the first flight it is HIGHLY! recommended to do the IMU calibration at least once. Even if there are no indications showing on the app. Many people who don't do this end up having issues later on specifically complaints about abnormal flying and unstable hovering all because they simply skipped over the initial IMU calibration. The reason behind this is that the IMU (Inertial Measurement Unit) measures and reports data such as angular velocity and attitude (including course angle, pitch angle, and roll angle). Using data provided by the drones accelerometer, gyroscope, thermometer, and barometer. Yes all of these measuring devices work together to determine the status of the aircraft and they all report their data to the IMU. To better understand its intricacies, look into the data measuring units placed inside our drones. Without doing a simple IMU calibration you are risking a lot of these measuring units being unable to communicate and measure effectively. After I received my unit the first thing i did was an IMU calibration, Gimbal calibration, Remote Controller Calibration and Compass. Do this at least once on a level ground without any magnetic interference around and the aircraft should run flawlessly.