 The sale was completed by the summer of 1973, by which time Delta had also realized the potential of Puerto Rico as a lucrative destination.Delta expanded its service to the Puerto Rican market during the mid-1970s, after decades of operating minimal service to San Juan.In the mid-1960s, Delta only flew one flight six days a week from San Juan to New Orleans with continuing, no-change-of-plane service depending on the day of the week to Dallas, Los Angeles and San Francisco.