Atlanta-based Delta pilot Captain Mark Kendall thought he was just thanking a Diamond Sky Mile club member on a recent flight.
Little did he know that his handwritten thank you note would become a viral Internet sensation.
Why? The woman to whom he wrote the note was Australian actress Claire Holt, who took a picture of the note and tweeted it to her more than 700,000 Twitter followers.
The tweet read: "Wow. Received this note from Captain Kendall on my flight today. Truly thoughtful. Treat him well @DeltaAssist!"
According to Yahoo, Holt is best known for her television work in "The Originals", "The Vampire Diaries" and "Pretty Little Liars."
The note written by Kendall reads:"Ms. Holt, Thank you for all your business as a Diamond Sky Miler. I appreciate how hard it is to be a Road Warrior, especially at this time of year, but I appreciate it."
Delta Air Lines confirmed to ABC that Kendall, a 25-year Delta pilot, wrote the note.
According to the ABC story, Kendall did not know Holt was a celebrity, only that she was a serious frequent flier.
Kate Modolo, a spokesperson for the airline, told ABC the airline encourages pilots to interact with passengers "when time permits." Kendall, she said, makes a practice of writing notes to passengers to thank them for their business whenever he has time.
Diamond status is the highest level of frequent flier membership in Delta's SkyMiles program. It requires 125,000 miles flown per year.