CHICAGO (AP) On Jan. l,an order went into effect requiring that every checked bag at more than 400 of the nation's commercial airports be screened for bombs and weapons.      Sunday was expected to the heaviest travel day since Jan. l. Yet spot checks on Sunday at several  of the nation's airports showed no major delays caused by the new security measures.     At the international terminal for Northwest Airlines at John F. Kennedy International Airport inprefix = st1 /New York, passengers waited up to 30 minutes longer than usual. Their bags were sent through giant screening machines and workers tore open taped boxes and searched through their contents before closing them up again.     Most travelers simply accepted stricter screening developed since the terrorist attacks on Sept. 11,2001,before which only 5 percent of the roughly 2 million bags checked each day were screened for bombs.      The U. S. government has put an additional 23,000 people into airports to carry out the new order.     Sonny Salgatar, a 23-year-old college student flying home to San Diego fromChicago, was told by an airport officer after the first pass that one of his bags was "hot", meaning there was something he couldn't identify and he wanted to open the bag for an inspection.     The "hot" item turned out to be Salgatar's clothing iron.     "Listen, anything they want to do for security is OK for me," Salgatar said. But not all of the passengers hold the same viewpoint as Salgatar's, complaining that they had to arrive at the airport too much time ahead of their schedule. The new measure was adopted to guard against.
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