But in the 1980"s you did not have interactive seat selection software. IIRC it was pull tab stick ons at the gate they put on to your Boarding Pass.
Unless you rode ALTAIR ( always late to arrive in Richmond)! You just piled on. After the co-pilot loaded the baggage, he climbed aboard, pulled up the door (the steps were in the door), took his seat and away you went.
Often the pilot or co-pilot checked you in also.