"Andai all'aeroporto per incontrare la coppia."
Translation:I went to the airport to meet the couple.
That's a long story.
In Northern Italy almost nobody would use "andai", even if they went twenty years ago to the airport.
In Southern Italy, people would use "sono andato" only if something happened 5 seconds before.
In theory "andai" gives a feeling of something that has happened in a past that is gone and has no more big influences on the present. "sono andato" should refer to something more recent.
You can use any of them, and people will understand.