The best open source Kalman filter code for Arduino is RTIMUlib, but any such filter will only determine the physical orientation and direction of travel of the glider (an Attitude and Heading Reference System, AHRS).
In order to navigate from one point to another, GPS is your only option for determining location and velocity.
Avoid GitHub - TKJElectronics/KalmanFilter: This is a Kalman filter used to calculate the angle, rate and bias from from the input of an accelerometer/magnetometer and a gyroscope. as it is NOT a Kalman filter, and doesn't work well.