A strike by air traffic controllers demanding better working conditions has shut down all airports in the country. The walkout began Thursday morning and affected international flights by the Salvadoran airline Taca, the Costa Rican national airline Lacsa, the Panamanian airline Copa, Pan American World Airways and the Honduran airline Sahsa. All domestic flights also were affected. The Air Traffic Controllers Union is demanding a salary review, improvements in training and an overhaul of equipment.