Ground workers at Pan American World Airways voted to end their four-week strike against the airline, which had threatened to fire thousands of employees. The agreement gives Pan Am the right to cut pensions, reduce health benefits, introduce part-time workers and offer lower starting salaries to persons hired in the future. It provides a 20% pay raise over three years and immediate bonuses of $600 to $1,000 as partial compensation for a 14% raise that the workers waived in 1982. Members of the striking Transport Workers Union voted 3,583 to 2,193 to ratify the pact. The airline still faces the threat of a strike by flight attendants, who have voted to walk out Monday.