NASA and Near Space Corporation (NSC) used a UAV as a High Altitude Shuttle System (HASS).

Drone Flight Tests FAA’s Technologies for Spacecraft Re-entry

A drone released from a high-altitude balloon carried a payload to evaluate how the equipment could help the FAA detect and track commercial spacecraft entering the National Air Space, NAS, as it descends from space.

Source: Drone Flight Tests FAA’s Technologies for Spacecraft Re-entry