The milestones, too, have tumbled. Most United games managed, 25 years in charge... and now, after taking the Reds to Southampton on Sunday, he has taken charge of his 1000th league game in English football.
It’s a phenomenal tally, especially when you consider Sir Alex had steered the Reds to victory in almost 60 per cent of them and tasted defeat just 168 times. In all, he's amassed a remarkable average of 2.03 points per game over his 26-year reign, and in that time, United have scored 1866 goals and conceded just 892, a goal difference of +974.
Here, we take a look at some of the ups and downs during his 26-years at Old Trafford...
The first Sir Alex started with a whimper, not a bang. In charge for the first time when United travelled to Oxford on 8 November 1986, he witnessed a poor performance and a 2-0 defeat. From there, the only way was up.
Most wins in a season: 28 (1999/00, 2006/07, 2008/09, 2011/12)
Fewest defeats in a season: 3 (1998/99, 1999/2000)
Consecutive clean sheets: 14 (15 Nov 2008 to 18 Feb 2009)
Most goals in a season: 97 (1999/2000)
Fewest goals conceded in a season: 22 (2007/08)
* All stats league games only