United ran out emphatic winners thanks to goals from Ashley Young, Juan Mata, Romelu Lukaku and Marcus Rashford.
Aboubakar Kamara replied for the visitors from the penalty spot.
But the defeat did not dampen the travelling fans’ spirit as they poked fun at United.
Fulham are bottom of the Premier League having lost a whopping ELEVEN of their 16 league games this season.
And they could he heard chanting: “You’re nothing special, we lose every week.”
The victory saw under-fire boss Jose Mourinho get back to winning ways in a week which has seen his own future at the club questioned.
His agent Jorge Mendes has moved quickly to play down the rumours that suggest he is set for the exit door.
And Mourinho said he was impressed with is side’s display.
He was particularly pleased with how they played in the first-half as they went in 3-0 in front at the break,
United slowed down in the second-half but managed to record their biggest win of the season.
“The first half was really good. We gave no chances to Fulham,” Mourinho said.
“We were strong, aggressive and intense. At times it was beautiful football. The first half was perfect.
“The second half was Ranieri’s fault. He made two changes that improved his team and gave us problems that we didn’t have in the first half.
“I also think there was some fatigue in some of my players. A few factors made the second half not as good as the first.
“We were intense without the ball and with the ball. Without the ball we pressed, we kept Mitrovic away from goal.
“With the ball it was simple, one or two touches. We were really good.
“We needed it. The last three matches we didn’t lose, but didn’t win.
“Now we have two away matches, then two at home. Let’s see if we can get more points from those matches.
“The players have shown they can be a better team than they are. When there is solidarity in the team, everyone giving their maximum, you attract more positive things.”