Bruno Fernandes and Edinson Cavani each scored twice as Manchester United thrashed an injury-hit Roma 6-2 at Old Trafford to close in on the Europa League final.
United are aiming to get to a final under Ole Gunnar Solskjaer at the fifth time of asking after four semi-final defeats in the past two seasons.
But only a second leg collapse will prevent them from facing Villarreal or Arsenal in Gdansk on May 26 after a stunning second-half performance.
The home side trailed at the break as Lorenzo Pellegrini's penalty and Edin Dzeko's tap-in cancelled out Fernandes's early opener.
But the Italians lost three players to injury before the break and United took full advantage.
Two predatory finishes from Cavani turned the tie around before Fernandes also fired home from the spot.
Paul Pogba and Mason Greenwood rounded off the scoring as United became the first team to score six goals in a European semi-final since Real Madrid in 1964.
"Very pleased with the response," said Solskjaer. "Second half we were very good."
With United realistically out of the Premier League title race, but also almost certain to secure a top-four finish, Solskjaer named his strongest available side as he aims to end a four-year trophy drought for the Red Devils.
The combination play between Pogba, Fernandes and Cavani consistently cut the Roma defence apart as they only marginally avoided a repeat of the 7-1 hammering they suffered at Old Trafford in the 2006/07 Champions League quarter-finals.
"We know we've got creative players, players who can create big chances, score goals, it's about getting them in the positions," added Solskjaer.
"Marcus (Rashford), Bruno, Paul, Edinson are all capable. The difference today is we took most of our chances."
In contrast to the vast majority of games this season, United came flying out the blocks and led after just nine minutes.
Pogba and Cavani teed up Fernandes, who dinked the ball over the advancing Pau Lopez for his 25th goal of the season.
Sitting seventh in Serie A, this competition represented Roma's last realistic chance to qualify for the Champions League next season and they reacted like a side whose season depended on it.
Pogba was penalised for handball as he slid in to try and block Rick Karsdorp's cross and Pellegrini confidently beat David de Gea from the spot.
Dzeko was a persistent thorn in United's side in four years as a Manchester City player and scored for the sixth time at Old Trafford when he tapped home Pellegrini's low cross on 34 minutes.
By that stage Jordan Veretout and Lopez had hobbled off injured and Leonardo Spinazzola followed before the break, leaving Roma without the chance to make any further substitutions in the second half.
"We had a good first half but we didn't exist in the second," Roma coach Paulo Fonseca told Sky Sport.
"It's difficult to explain how the same team that did so well in the first half had that kind of second half."
Another fine team move involving Pogba, Fernandes and Cavani ended with the Uruguayan firing into the top corner three minutes into the second half.
Cavani was then in the right place for a tap-in when substitute goalkeeper Antonio Mirante parried Aaron Wan Bissaka's shot into his path.
Chris Smalling had a night to forget on his return to Old Trafford, but was harshly penalised when he clashed with Cavani as a ball flashed across the Roma goal.
Fernandes was clinical from the spot to give United breathing space.
The Portuguese turned provider for Pogba to power home a header 15 minutes from time.
And Greenwood landed the final blow as he rounded off a counter-attack thanks to some more weak goalkeeping by Mirante.
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