"Data show that 50 (38 percent) of the 130 pilots-in-command (PICs) of the accident aircraft held commercial pilot certificates, and 30 PICs (23 percent) held airline transport pilot (ATP) certificates (Table 8). Of the 50 PICs with commercial pilot certificates, 20 PICs had been cautioned about wake turbulence by ATC. Of the 30 PICs with ATP certificates, six PICs had been cautioned about wake turbulence by ATC. Pilots with private pilot certificates flew the trailing aircraft in 36 (28 percent) of the 130 accidents; 12 pilots had been cautioned about wake turbulence. Of 14 student pilots (11 percent) who flew the trailing aircraft in wake-turbulence accidents, seven pilots had been cautioned about wake turbulence."