Aircraft from all four U.N. services were a mixture of propeller-driven and jet aircraft, and in general the propeller aircraft launched up to an hour earlier than the jets to coordinate their arrival over the target together. The carriers launched their propeller aircraft at 14:00 and their jets at 15:00. Air Force fighter-bombers, having the longest distance to fly, took off at 14:30. Because the Sui-ho Dam was located less than forty miles (65 km) from the MiG 15 fighter base complex at Antung/Tai Ton Chao/Phen Chen in China, where 150 MiGs had been counted by the weather reconnaissance, a coordinated simultaneous arrival over the targets was crucial to limiting the effectiveness of any defensive reaction.