I wonder if it would be practical to install upwards facing antennas on cell tower and then have a tracking dish on planes track these to cut out the satellite when over (populated) ground. If a line-of-sight microwave link could be established, it should be possible to have high-bandwidth low-latency connectivity in the air.

What is the effective beamwidth of a microwave antenna that needs to maintain a 50-100km link? Would the ground antennas need to be tracking as well?