SYDNEY (AFP) - Hundreds of flights were grounded Tuesday in Sydney, Melbourne, Adelaide and Canberra as the Chilean ash cloud returned to Australia with a vengeance, with the chaos due to worsen over coming days. The cloud, created by the eruption of the Puyehue volcano high in the Andes more than two weeks ago, has looped the globe and made its way back Down Under to wreak fresh havoc. State broadcaster ABC said the travel plans of more than 120,000 people had been thrown into disarray -- with an industry group saying it was Australia's worst air travel disruption for more than 20 years.