One Florida mom is feeling grateful after a kind stranger on her American Airlines flight offered his first-class seat to her and her baby daughter traveling to the Children's Hospital of Philadelphia. She expressed her thanks in a Facebook post that has since gone positively viral with over 261,000 likes.

On Dec. 6, Kelsey Zwick boarded American Airlines flight 588 from Orlando to Philly with Lucy, one of her 11-month-old twin daughters. Zwick told Fox News that little Lucy and her identical twin, Eva, were born 11 weeks prematurely, at just 29 weeks gestation, and that Lucy suffers from severe chronic lung disease as a result of Twin to Twin Transfusion Syndrome (TTTS), a complication of the pregnancy.

The brave baby girl was on oxygen support “24/7” until recently, Zwick says. Today, Lucy only needs oxygen at night and while flying – when one small good deed reminded Zwick how “blessed” she and her husband, Yuri, truly are.

“To the man in 2D. Today you were traveling from Orlando to Philly. I don’t know you, but I imagine you saw us somewhere. I was pushing a stroller, had a diaper bag on my arm and also lugging an oxygen machine for my daughter,” Zwick began her much-buzzed-about Facebook post. “We had smiles on our faces as we were headed to see her “friends” at CHOP.

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“We pre-boarded the plane, got cozy in our window seat and made jokes to those around us about having to sit by my yelling-but-happy baby. The flight attendant came over and told me you were waiting to switch seats. You were giving up your comfortable, first class seat to us,” she wrote.

“Not able to hold back tears, 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,” the mom continues.

“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,” Zwivk mused. “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.”

Zwick’s emotional story evidently touched the hearts of many, sparking many supportive comments on the post that has since been shared over 164,000 times.

Moving forward, she told Fox News that the generosity of her fellow American Airlines passenger has since inspired her to “reflect,” and want to “pay it forward.”

“When the flight attendant mentioned that the man in first class wanted to switch. It took me a moment to understand why. As it sunk in that a perfect stranger wanted to bless us, I couldn’t hold back tears. It was a gesture of someone saying, I SEE you and this is what I can do,” Zwick said on Dec. 8.

“As I sat in the roomy seat, I couldn’t help but reflect. First, the long road on not knowing if we could have children of our own. We got pregnant and were diagnosed with TTTS, a rare complication. Overnight we had to fly across the country to get a fetal surgery when I was pregnant,” she revealed. “We didn’t know if they would survive the procedure but these girls our fighters! They did amazing!”

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When the twins were born on January 13, Eva arrived in the world crying and breathing while Lucy was blue and “very sick,” Zwick says, and the newborn was immediately placed on maximum support for her lungs. The twins proceeded to spend nearly three months in the NICU at Winnie Palmer Hospital in Orlando – but gained enough strength to have the medical clearance to go home.

“WE are the lucky ones,” Zwick says of the joy that she and her husband were able to bring their girls home.

Now, the twin's mom says that she hopes others are inspired to go out and do good for others after hearing their story.

“You never know what people are going through. So many people helped us along the way from family and friends to the TTTS foundation to the man in 2D. One small act of kindness is a ripple effect!” she said. “[And] when you get to the other side of your struggle – whatever that looks like – pay it forward!”

“Thank you to the man in 2D! The world is hungry for kindness... and I hope this expands far beyond what happened to us yesterday,” she concluded.