It was 1988, and Mary Andersen was at the Miami airport checking in for a long flight to Norway to be with her husband when the airline representative informed her that she wouldn't be able to check her luggage without paying a 100 surcharge:

When it was finally Mary’s turn, she got the message that would crush her bubbling feeling of happiness.
-You’ll have to pay a 103 dollar surcharge if you want to bring both those suitcases to Norway, the man behind the counter said.
Mary had no money. Her new husband had travelled ahead of her to Norway, and she had no one else to call.
-I was completely desperate and tried to think which of my things I could manage without. But I had already made such a careful selection of my most prized possessions, says Mary.

As tears streamed down her face, she heard a "gentle and friendly voice" behind her saying, "That's okay, I'll pay for her."

Mary turned around to see a tall man whom she had never seen before.
-He had a gentle and kind voice that was still firm and decisive. The first thing I thought was, Who is this man?
Although this happened 20 years ago, Mary still remembers the authority that radiated from the man.
-He was nicely dressed, fashionably dressed with brown leather shoes, a cotton shirt open at the throat and khaki pants, says Mary.
She was thrilled to be able to bring both her suitcases to Norway and assured the stranger that he would get his money back. The man wrote his name and address on a piece of paper that he gave to Mary. She thanked him repeatedly. When she finally walked off towards the security checkpoint, he waved goodbye to her.
Who was the man?

Barack Obama.