SEOUL, South Korea — A passenger plane burst into flames Sunday after it skidded off a runway at a South Korean airport and slammed into a concrete fence when its front landing gear apparently failed to deploy. Most of the 181 people on board died in one of the country’s worst aviation disasters. [time-brightcove not-tgx=”true”] The Jeju Air passenger plane crashed while landing in the town of Muan, about 290 kilometers (180 miles) south of Seoul.