After stealing the jet in Russia, Harm and Mac are shot down, but then saved by a gypsy brother and sister, who help Harm learn the truth about his father.
Harm finally gets to learn the truth about his father. Quite a few things Harm and Mac do are unrealistic, but Harm has a fire in his belly when it comes to his dad and the truth; most children do.
If only every child could learn the truth like Harm did. But there are still many families that know nothing.
I assume Harm Sr. knew that would be considered MIA and his family would hear this and eventually move on. He probably had to do the same.