Booed throughout his return to Arsenal, Alexis Sanchez responded to the rancor with a rare goal for Manchester United and reveled in the celebrations.
The forward's fifth goal in 33 appearances since leaving Arsenal a year ago set United on their way to a 3-1 victory to book a place in the fifth round of the FA Cup.
With Jesse Lingard and Anthony Martial also scoring, Ole Gunnar Solskjaer reeled off a club-record extending eighth successive victory in all competitions at the start of his reign since replacing the fired Jose Mourinho in December.
With only a short-term contract on loan from Norwegian club Molde until the end of the season, Solskjaer is making it increasingly hard for United to consider any other option for their fourth permanent appointment since Alex Ferguson’s retirement in 2013.
Revitalised United were rarely troubled by an Arsenal side that beat Chelsea last weekend. Electric on the break, the visitors couldn't be contained at times by the hosts.
When Romelu Lukaku slipped the ball through to Sanchez in the 31st minute, the Chile forward took the ball around goalkeeper Petr Cech before placing it in the net.
Sanchez raised his arms aloft to the Arsenal fans who had targeted him with jeers.
They had little to cheer. Not after Arsenal fell further behind inside two minutes after timidly giving United too much space. Luke Shaw worked the ball out from defense before releasing Lukaku on a run down the left flank. The forward completed the counterattack by squaring for the unmarked Lingard to sidefoot into the net.
Arsenal had a glimmer of hope in the 43rd when Aaron Ramsey weaved in from the left and put the ball through Eric Bailly's legs across to Pierre-Emerick Aubameyang for a tap-in.
Having already lost Sokratis with an ankle problem in the first half, Arsenal's defensive injury problems deepened after the break when Laurent Koscielny was forced off after his jaw by caught by Lukaku.
United couldn't be sure of there progress until Martial netted in the 82nd after Paul Pogba's attempt was parried.
There was a fiery conclusion when Arsenal defender Sead Kolasinac squared up to United forward Marcus Rashford, setting off a melee that spilled off the pitch close to fans.
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