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PHILADELPHIA (CBS) – A woman is looking to thank a mystery passenger who gave up his first class seat during a flight to Philadelphia.

Kelsey Rae Zwick and her daughter, Lucy, were traveling from Orlando to Philly for treatment at Children’s Hospital of Philadelphia. Zwick says she and Lucy had already boarded American Airline Flight 588 when they were informed by a flight attendant that a passenger in first class wanted to switch seats.

The touching gesture brought tears to Zwick’s eyes.

“I cried my way up the aisle while my daughter Lucy laughed! She felt it in her bones too… real, pure, goodness. I smiled and thanked you as we switched but didn’t get to thank you properly,” says Zwick in a Facebook post. “Sooo… thank you. Not just for the seat itself but for noticing. For seeing us and realizing that maybe things are not always easy. For deciding you wanted to show a random act of kindness to US. It reminded me how much good there is in this world.”

Zwick says she hopes to one day tell her daughter the story, but in the meantime she hopes to pay it forward.