It was the first meeting of the two sides on the airline's demands for $490 million in wage cuts and other concessions from its 38,000 employees. Two representatives of one of the unions, the International Assn. of Machinists, walked out of the talks after 10 minutes because the airline refused to sign a statement saying that the talks did not constitute a reopening of the IAM's contract. Representatives of the Teamsters Union and the Air Line Pilots Assn. remained at the meeting.