Ighalo was handed his full debut for the club since arriving on loan after Anthony Martial sustained a muscle injury in training.
Scott McTominay also made his long-awaited return to action having been sidelined since December as United named a strong line-up.
And they were on the pulse from the first whistle, testing Simon Mignolet with two chances inside the first five minutes with Fernandes and Mata both forcing a save from the Belgian.
United were fortunate not to concede a penalty when Harry Maguire appeared to pull down David Okereke in the penalty area, but neither the referee nor VAR opted to intervene.
Fernandes was enjoying an influential role through the middle and saw another effort saved by Mignolet before playing a part in the opener. The playmaker found Daniel James with a clever backheel and the Welsh winger’s effort was bizarrely saved by Brugge defender Simon Deli.
Referee Serdar Gozubuyuk pointed to the spot and pulled out a red card, which seemed like the obvious decision. The Turkish official was told to review the decision on the VAR monitor but, after two minutes of deliberation, decided not to change his mind.
Fernandes stepped up and with a hop and a skip, sent Mignolet the wrong way to net his second penalty in the space of five days.
The floodgates opened all too quickly and United were feeling rampant. Fernandes was involved again for the second, clipping a lovely pass to the back post and Juan Mata’s cutback found Ighalo, who couldn’t miss from four yards out.
United were in complete control and the scoreline soon reflected it when Scott McTominay struck home from the edge of the box after good work from Fernandes and Fred.
It was no surprise to see United take their foot off the gas in the second half and Fernandes received a deserved standing ovation when substituted midway through the half.
United finally added a fourth eight minutes from time when substitute Jesse Lingard unselfishly set up Fred before the Brazilian added a second in injury time as United cruised into the next round, with the mood certainly improving at Old Trafford.
Man Utd manager Ole Gunnar Solskjaer speaks to BT Sport:
What he was happy with? “The football we played at times. First half, I thought we started the game with great intensity. Tempo with our game , combination play, good rhythm with our game. Very happy. “
“” The goal was a good example of what you want from Odion. The ball’s come over him and it spins quickly, gets over the center back and taps it in . What we’ve been lacking a little recently. “
More from Ighalo …
“The confidence was high, we spoke about that before the game that it’s played at home and the fans are behind us . We had to go all out from the first minute and push to go to the next round and we did.
The first goal opened up everything and the red card made it difficult for them, with our attacking and playing at home too. From the start, we worked hard until the last minute. “
We’ll have the post-match reaction for you shortly, so stick with us!
James Robson on a stellar night for Manchester United …