Ferguson will overtake Busby's record of 24 years, one month and 13 days in the job when he takes his Premier League leaders to champions Chelsea on Sunday.
Busby accumulated his 8,800-plus days in charge as United manager in two spells, the first between 1945 and 1969 when he built the modern club and made them champions of Europe, and the second spell a largely forgettable postscript in 1970/71.
Ferguson has been in control at Old Trafford since November 1986 but if he had been starting in the current football climate, it is unlikely he would have survived this long.
It took Ferguson nearly four years to bring his first trophy to Old Trafford and as this month's sackings of Newcastle United's Chris Hughton and Blackburn Rovers' Sam Allardyce prove, that is too long to wait for success these days.
Hughton was shown the door after 14 months in the job, while Allardyce was in his for two years and was fired only a month after the arrival of new owners in a move Ferguson branded "a stupid decision" that "confounds common sense".
The quick-fix mentality of some clubs contrasts with the longevity that 68-year-old Ferguson has achieved at United - and previously at East Stirling, St Mirren and Aberdeen in Scotland, after surpassing 2,000 games as a manager in professional football in October.
"To pass 2,000 games and now become the club's longest-serving manger this season is a such fantastic achievement and surely one that will never be equalled in the future," League Managers Association chief executive Richard Bevan said in a statement on Friday.
LAST CHANCE
Ferguson's first United game in charge was a 2-0 defeat by Oxford United on November 8, 1986 and after three years of mediocrity there were growing calls from fans and the media for his dismissal.
The Scot has called December 1989 the "darkest period" he had suffered in the game and a month later an FA Cup Third Round match against Nottingham Forest was seen by many as his last chance to save his job.
United famously won the match with a goal from Mark Robbins and a few months later won the FA Cup with the European Cup Winners Cup following a year later.
From then on Ferguson could do no wrong, ending a 26-year wait for the championship in 1993 and reaching the pinnacle with the Champions League triumph and treble in 1999.
He has won a total of 11 league titles, five FA Cups, four League Cups and two Champions League titles at United - more trophies than Busby achieved, but complementing Busby's successes, not overshadowing them.
Bobby Charlton, who played under Busby from the 1950s to the 1970s winning the European Cup in 1968, has been a United director throughout Ferguson's time and said the Scot's future had never been in doubt -- even during the dark period and that other clubs could learn from that.
"Half the problems that people get into is the fact that they get rid of managers too soon. We would not make that mistake," he said on the club's website.
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