Complex sentence: This Vessel is mostly used on the Seattle-Bremerton route however, sometimes she is found on the Fautleroy-Vashon-Southworth run and the Mukilteo-Clinton Route filling in for its sister ships.
Split into simpler sentences: This Vessel is mostly used on the Seattle-Bremerton route. However, she is sometimes found on the Fautleroy-Vashon-Southworth run and the Mukilteo-Clinton Route filling in for her sister ships.