50 years ago today when the passenger in seat 18c, one "Dan Cooper" by his own account, leaped off the aft staircase of Northwest Airlines Flight 305 with $200,000 in ransom money.  It was - like today - Thanksgiving Eve. Roger McGuinn and his lyricist, Jacques Levy, wrote a song about it - "Bag Full of Money" - in the vein of Woody Guthrie's "Pretty Boy Floyd". In July of 1972, he and the remnants of the Clarence White-era Byrds recorded it. A year later Roger re-recorded it for his first solo album. Dan -or D.B. as he is commonly, mistakenly known, was never found, but in 1980 almost $6,000 in disintegrated, rubber band bound bills were, on the banks of the Columbia River near Vancouver, WA.   Maybe he survived the jump, but - landing in the river - the money was lost with most of it washing out to sea. That might explain the 1980 recovery. More likely he perished in the attempt, ended up impaled atop a tall pine. I know it's wrong, because threa