On November 24, 1971 (in one of the most well-known and infamous incidents in aviation history), a skyjacker known as "Dan Cooper" (later mistakenly renamed "D.B. Cooper") parachuted in a rainstorm from a Northwest Airlines 727 jetliner over rugged terrain somewhere between Seatle, Washington and Reno, Nevada. He had been given $200,000 ransom money in $20 notes. Before handing over the ransom to the hijacker, the serial # of each bill was copied down. No trace of the hijacker was ever found, and none of the bills have ever shown up in circulation. This is the only unsolved skijacking in history.

The only ransom money ever discovered was found on February 10, 1980 along the banks of the Columbia River near Vancouver, Washington by Brian Ingram, then an eight-year old boy on vacation with his parents. The estimated $5,800 of recovered notes were turned over to the FBi. Eventually, only a small portion of the notes were returned to the Ingram family.

I purchased a partial 1963A $20 bill from Brian Ingram. The serial # on the bill appears on the FBI list of bills.

There is a great show on the National Geographic channel about the crime:

http://channel.nationalgeographic.com/episode/the-skyjacker-that-got-away-4375/Photos#tab-Overview

If you are interested in the case - watch it. I believe it is the best explanation on what happened to Cooper and how the $ recovered made it to where it was found.