Ryan Giggs inflicted more misery on struggling Birmingham as Manchester United coasted to a comfortable victory at Old Trafford.
Manchester United celebrate their first goal against Birmingham
Birmingham keeper Maik Taylor was only able to help the Welshman's free-kick over the line as United broke the deadlock in the third minute.
Giggs then latched onto a through ball from Wayne Rooney to tuck in a second after 15 minutes.
Rooney sealed the win, racing through to score with eight minutes left.
The game was watched by a Premiership record attendance of 69,070.
Less than a week after being hit for seven by Liverpool in the FA Cup, a trip to Old Trafford would have been an unappetising prospect for Steve Bruce's relegation-threatened Blues.
Their worst fears were realised inside three minutes when Martin Latka brought Cristiano Ronaldo down 25 yards out.
With Ronaldo and Rooney hovering over the ball, Giggs hit a precise shot that Taylor was only able to tip onto the inside of the post and into the net.
The Blues would have to be credited for the battling spirit they showed afterwards.
While capitulation at the end of their week from hell would have been understandable, they went in search of a way back into the game.
Edwin van der Sar had to react smartly to tip Emile Heskey's header wide and DJ Campbell also tested the United keeper.
But the abiding memory of the first half an hour will have been United's dynamic play with Rooney and Ronaldo in their element as they displayed some devastating footwork.
Rooney's passing and movement was exemplary and, after being fed by Giggs, he hit a perfectly weighted pass to the Welshman who did the simple bit and tucked home the second with 15 minutes on the clock.
Rooney should have got on the scoresheet himself but squandered two clear-cut chances after being put through by Ronaldo.
While never looking in danger of allowing a Birmingham comeback to spoil skipper Gary Neville's 500th appearance for the club, United did lack the zip after the break that had characterised their first-half efforts.
Birmingham enjoyed more possession but despite earning plenty of corners and applying some pressure, they could not find a way back into the game.
Stephen Clemence did fire narrowly wide but his effort, from long distance, was characteristic of the Blues' afternoon.
Then Rooney raced through and was not going to make a third mistake as he fired the ball past Taylor.
Man Utd: Van der Sar, Neville, Ferdinand, Vidic, Silvestre, Ronaldo, O'Shea, Giggs (Fletcher 77), Richardson (Park 39), Rooney, Saha (van Nistelrooy 73).
Subs Not Used: Howard, Evra.
Goals: Maik Taylor 3 og, Giggs 15, Rooney 83.
Birmingham: Maik Taylor, Melchiot (Tebily 82), Cunningham, Latka, Lazaridis (Bruce 87), Jarosik, Clemence, Johnson, Pennant, Heskey (Kilkenny 87), Campbell. Subs Not Used: Vaesen, Forssell.
Booked: Latka, Jarosik, Pennant.
Ref: M Dean (Wirral).