To extend the altitude range beyond the defaults, you need to tap and hold the Altitude slider for 8 seconds (while remaining very still).
The range can currently be extended to 10 meters to 300 meters. We do not enable this by default since it is not something we recommend doing. 10 meter flights greatly increase the chances of hitting something and anything above 120 meters is not legal in the United States and a lot of other countries. If you wish to extend the range you may do so at your own risk.