Complex sentence: The Piedmont name was resurrected in 1993, when USAir (now US Airways) renamed Henson to "Piedmont Airlines", to protect the Piedmont brand name, which could be used by others if not exercised in trade use for a period of time.
Split into simpler sentences: The Piedmont name was resurrected in 1993, when USAir (now US Airways) renamed Henson to "Piedmont Airlines". This was done to protect the Piedmont brand name, which could be used by others if not exercised in trade use for a period of time.