Here's a link to the Buddy Holly Center here in Lubbock.
http://www.buddyhollycenter.org/
And a link to a reprint of the original article in the evening Lubbock AJ on February 3, 1959, reporting the crash.
http://www.buddyhollyarchives.com/crash1.shtml
Jennings told CMT.com that the brutal crash left scars that still haunted him 40 years after Hollys death. Jennings never came to terms with his last words to Holly, the joking refrain, "I hope your ol' plane crashes."
There have been a number of people over the years who have claimed they had given up a seat on that plane. Just as there have been a number of people who have claimed they had been asked to join the Rolling Stones after Mick Taylor left in mid 1970s. A nice thing to add to your resume, but I see no reason to believe any of them.