The Boeing 720-059B HK-726 “Nariño” first flew on March 24, 1965, and was delivered to Avianca on April 8, 1965.
“Nariño” later served with several other airlines, including Monarch Aviation, Jet Star Inc., and Silver Wings, before it was bought by Boeing on October 2, 1984. Boeing put the aircraft to use in the KC-135E military programme.
HK-726 was finally broken up in March 1991.
“Classic Early Jet Liners 1958-1979”.
- http://www.airteamimages.com/boeing-720_HK-726_avianca_179949_large.html (the same as on my book).