Bonus Question (for Nov. 2 homework)

The following quote is the beginning to Don McLean's "American Pie" (recently covered by Madonna):

A long, long time ago...
I can still remember
How that music used to make me smile.
And I knew if I had my chance
That I could make those people dance
And, maybe, they’d be happy for a while.

But February made me shiver
With every paper I’d deliver.
Bad news on the doorstep;
I couldn’t take one more step.

I can’t remember if I cried
When I read about his widowed bride,
But something touched me deep inside
The day the music died.

What historical event was he referring to here? I.e., which day is called the "day the music died"?