Just noticed today that the program has been extended until Jan. 2005!!! Check gleff's same link above.
A couple details:
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Register to participate in ATA's Anniversary Travel Awards program at ata.com.
Purchase your tickets at ata.com using your Travel Awards ID# and travel before January 31, 2005
Qualifying flight activity completed between September 30, 2002, and June 30, 2003 is now valid toward award redemption through January 31, 2004.
Qualifying flight activity flown after July 1, 2003 is valid toward redemption through January 31, 2005 </font>