This was a superb team display and was encapsulated in another supreme performance from Wayne Rooney.
He scored United's opener after 53 minutes and made the second for Ji-Sung Park 14 minutes later, but his all-round display showed a class well beyond his 20 years.
United's first goal stemmed from a decisive tackle from Nemanja Vidic on Robin van Persie on the left.
The ball fell for Mikael Silvestre who picked Rooney out in the Arsenal box with a pin-point cross from the wing.
Rooney's excellent control saw him take the ball down on his chest and flash a right-foot shot from 12 yards beyond Arsenal goalkeeper Jens Lehmann into the roof of the net.
But, against a team like Arsenal, United needed a second goal and it came with 13 minutes left, Rooney again instrumental in its creation.
Gary Neville's measured pass down the right sent Rooney racing clear of Philippe Senderos.
The Swiss central defender touched his heels as he raced into the box, but Rooney kept his feet, looked up and squared the ball from the by-line to the far post, where the unmarked Park was left with a simple tap-in from two yards out.
Had United not scored their two second-half goals, more would have been made of the incident three minutes before the interval when they should have had a penalty and Arsenal central defender Kolo Toure should have been sent off.
Ruud van Nistelrooy's through ball sent Rooney clear and, and as he rounded the advancing Jens Lehmann, he got in a shot 12 yards out from the left side of the Arsenal box.
With the ball heading goalwards, Toure launched himself full length to scoop the ball on to the post beyond Senderos. Referee Graham Poll allowed play to continue and Toure escaped unpunished.
Arsenal's strong opening could have easily produced a goal but for United goalkeeper Edwin Van der Sar who twice saved well from Van Persie.
But United weathered the storm and Rooney twice tested Lehmann at the other end, first with a scorching 25-yard drive and then with an effort which saw the German goalkeeper turn the ball away one-handed in the 25th minute.
The second half saw united take control and even the introduction of Thierry Henry as a 69th minute substitute for van Persie failed to fire the Gunners to raise their game.