The People's Republic of China makes free use of the number 4 in many military designations for People's Liberation Army equipment, with examples including the Dongfeng-4 ICBM, Type 094 submarine, and Type 054A frigate, although the practice of starting aircraft designations with 5 leads some to speculate that it avoids the starting numeral 4 for aircraft designations much as the United States avoids use of the number 13 in that context. By contrast, the navies of the Republic of China (Taiwan) and of South Korea refrain from using the number 4 when assigning pennant numbers to their ships.