Traveler's good deed: Stranger gives first-class seat to Florida mom with baby

Kelsey Rae Zwick has been overwhelmed the past few years.

She and her husband have twin daughters, Lucy and Eva, who had complications at birth and were born at 29 weeks, Yahoo News reported. The infants spent their first few months in the neonatal intensive care unit, followed by months of treatments.

Lucy and Eva suffer chronic lung disease from the intubation period. Because she had other complications, Lucy had also started treatment at the Children’s Hospital of Philadelphia.

Zwick was on an American Airlines flight from Orlando to Philadelphia on Thursday with Lucy, who was yelling and yakking away, when a flight attendant came over and told her a man in first class wanted to switch seats with her, Yahoo News reported.

Zwick was stunned. She was not able to thank the stranger when they arrived, so she posted on social media, hoping to pay the act of kindness forward.

"I guess it was his birthday, and he did reach out to us," Zwick told Yahoo News. "He was thanking me for a birthday to remember. It was the best day. He said it made him and his wife cry, and he said, 'I am so glad we were on the same flight.'"

Zwick appreciated not only the additional space for Lucy’s oxygen machine and the first class accoutrements, like the cheese plate, but also the gesture.

"Sooo... thank you. Not just for the seat itself but for noticing. For seeing us and realizing that maybe things are not always easy," she wrote. "For deciding you wanted to show a random act of kindness to US. It reminded me how much good there is in this world. I can't wait to tell Lucy someday. In the meantime... we will pay it forward."