According to the NFL, the Hail Mary pass from over 40 yards has about a 2% chance of success. Last season saw a record number of Hail Mary plays (9) succeed in college football including Houston’s Hail Mary against BYU as the half ran out in Provo. (Remember that one?) This one against Nebraska was the 2nd time BYU has successfully completed the play. Nebraska had a successful Hail Mary against Northwestern in 2013. Since 2000, there has been at least one successful Hail Mary every season. Although the list at Wikipedia is incomplete.
The name of the play is credited to Drew Pearson of the Dallas Cowboys in a playoff game against the Minnesota Vikings in 1975. Pearson said that when Roger Staubach threw the ball to him, he closed his eyes, said a Hail Mary and came down with the ball. The Cowboys tried the play again in the Super Bowl against the Pittsburgh Steelers but this time the ball bounced off of Pearcy Howard’s helmet.
Jim McMahon’s pass to Clay Brown in the 1980 Holiday Bowl was the first time a successful Hail Mary, as we know it today, was completed at the collegiate level.