Australia's national air carrier, Qantas, has grounded its planes until it can reach an agreement with unions on pay and working conditions. The move will affect 70,000 passengers and is expected to cost the company $20 million a day. Australian Prime Minister Julia Gillard, who is stranded in Perth, called for an end to the dispute and said the grounding of the fleet could have implications for the economy. The strike comes at an especially bad time for Australia. Nearly 20 world leaders are in Perth for the Commonwealth Heads of Government Meeting, and tens of thousands of Australians are using the weekend to travel for Tuesday's Melbourne Cup horse race.