In a statement to The Gazette in Colorado Springs, an Air Force Academy spokesman didn't specify what violation led to Hammond's drop in status.
"Donald Hammond is no longer a cadet in good standing and cannot represent the academy in outside activities," Air Force said in a statement.
The Gazette reported that other student-athletes who had dropped in status in the past missed at least one season of competition.
Hammond, a senior from Hampton, Georgia, started 11 of 13 games while leading the Falcons to an 11-2 record in 2019. He ran for 553 yards with 13 touchdowns, while passing for 1,316 with 13 more scores.
Hammond's 177.88 passing efficiency mark in 2019 ranks second in Air Force history for a single season. He became the first Falcons quarterback since Dee Dowis in 1989 to throw for more than 300 yards in a game when he had 327 with four touchdowns in a 44-22 win at New Mexico on Nov. 23.
The Falcons lost two senior backups after the 2019 season, and juniors Warren Bryan and Chance Stevenson and sophomores Haaziq Daniels, Zachary Larrier and Max Massingale were competing behind Hammond.