Aviaco was always linked to Iberia. First, because both of them used to belong to INI (later known as SEPI). Second, because IB
was always like "the parent company" which partially controlled AO's operations, and third because they completely took over Aviaco in recent years.
In fact, during the late 80s and early 90s, Iberia did their first tests about having a "hub" for Central American flights somewhere between Miami and the Dominican Republic, and for that purpose they placed an Aviaco DC9 in Santo Domingo. A DC-10 used to fly from MAD
carrying pax that would later connect to Central America being on the DC9. It lasted only for about 1 year before they moved their operations to MIA
Also during the years that IB
DC9s operated to Central America from the famous (now disappeared) MIA
"hub" (before being replaced by MD87s and later by A319s) it was common to see Aviaco's DC9s among them...In fact, when I moved to Guatemala in 1998 (stayed there until 2003) I arrived there onboard one of AO's DC9s.