Douglas Aircraft Co. in Long Beach has indefinitely suspended about 300 workers, including deposed United Auto Workers Local 148 President Bob Berghoff, for failing to return to work despite warnings. Douglas spokesman Don Hanson said slowdowns have put the firm weeks behind schedule on aircraft deliveries to airlines. Many of the suspended workers spent the time taken from their jobs in federal court, where they joined Berghoff in challenging the takeover of their local by UAW International. The Detroit-based international union took control of Local 148 two weeks ago after a hearing on alleged improprieties in the local's aborted May 12-13 election. Local 148, which represents about 9,500 of the 22,000 workers at Douglas' Long Beach plant, has spent the last nine months in contract negotiations, which are stalled on the issues of medical insurance payments and reorganization of work duties.