In 1967, an Italian man boarded a flight from Zurich to New York with a rather unusual traveling companion. She had her own first-class window seat, a ticket under the name “Mrs. Modestini”, and also happened to be nearly 500 years old.

You see, “Mrs. Modestini” was actually Ginevra de’ Benci, a painting by Leonardo da Vinci that had just been purchased for a reported $5 million. And the man sitting beside her, art conservator Mario Modestini, had one job: get her safely to Washington DC.

Easier said than done.

Leonardo had painted Ginevra on wood, and for years she'd been kept in a chilly castle cellar in Liechtenstein. A sudden change in temperature or humidity could warp the wood or crack the paint.

Not exactly the kind of thing you'd want happening to a $5 million painting.

So Modestini came up with a clever solution: a $52.95 American Tourister suitcase, lined with Styrofoam, with the painting carefully sealed inside layers of plastic and a plywood box. He even fitted it with a temperature gauge so he and National Gallery official Ernest Feidler could keep an eye on things without opening the case.

Then, just when things seemed to be going smoothly, a snowstorm delayed their landing in New York by five whole hours.

“I would be less than truthful if I didn’t say that I had apprehensions”, Feidler later told TIME.

Fortunately, the painting made it through. FBI agents met the group in New York, and a private plane carried their precious passenger on to Washington. There, the suitcase was finally opened, and Leonardo's nearly 500-year-old masterpiece was found safe and sound.

When Ginevra de’ Benci went on display, nearly 1,000 people came to see her in the very first hour.

And here's something worth remembering to this day, she's the only Leonardo da Vinci painting in the Americas. You can find her at the National Gallery of Art in Washington, where, if you look closely, you can even spot Leonardo's fingerprints in the paint.

And the best part? This woman needed a $417 first-class ticket to get to Washington. You can go see her for free.