Workers at Rio de Janeiro’s two airports went on partial strike at midnight on Wednesday, on the eve of the opening game of the World Cup in Brazil. Rio’s Galeao international airport isexpected to be one of the country’s busiest during the month-long tournament. The walkout also affects Santos Dumon airport, which provides domestic service, including flights to Sao Paulo, where thefirst World Cup game will be held on Thursday. Unions said only 20 percent of workers at the two airports would walk off the job for 24 hours initially. The workers are seeking raises of at least 5.6percent.