Complex sentence: Unmanned aerial vehicles (UAVs) are also used for much aerial reconnaissance in the 21st century, being able to overfly hostile territory without putting human pilots at risk, as well as being smaller and harder to detect than man-carrying aircraft.
Split into simpler sentences: Unmanned aerial vehicles (UAVs) are also used for much aerial reconnaissance in the 21st century. They have the advantage of being able to overfly hostile territory without putting human pilots at risk, as well as being smaller and harder to detect than a man-carrying aircraft.