Kammala jumla mai zuwa: A watan Oktoba na shekarar 1965, an kafa rundunar sojin sama ta Amurka (USAF) ta 20 a sansanin Tan Son Nhut Air a Kudancin Vietnam, wanda aka fara da jiragen sama na CH-3C. A watan Yunin 1967 UH-1F da UH-1P suma an kara su a cikin kayan aikin naúrar, kuma a ƙarshen shekara an sauya dukkan rukunin daga Tan Son Nhut zuwa Nakhon Phanom Royal Thai Air Force Base, tare da CH-3s da aka tura zuwa Helicopter Squadron na 21. A ranar 1 ga Agusta 1968, an sake sanya wannan rukunin a matsayin 20th Special Operations Squadron. An san UH-1s na SOS na 20 a matsayin "Green Hornets", wanda ya samo asali ne daga launi, an yi amfani da shi a cikin launin kore mai launin launin fata (kore da launin ruwan kasa), da kuma kiran kira na rediyo "Hornet". Babban aikin wadannan jirage masu saukar ungulu shi ne sakawa da kuma fitar da kungiyoyin bincike, samar da rufin asiri ga irin wadannan ayyukan, gudanar da yakin basasa, da sauran ayyukan tallafi ga ayyukan sirri musamman a Laos da Cambodia a lokacin da ake kira
Yaƙin Sirri.