Bruno Fernandes and Edison Cavani scored two goals apiece as Manchester United came from behind with five second-half goals to thrash Roma 6-2 in the Europa League semi-finals.
But there was little joy for Arsenal, the other Premier League club who went down 2-1 to Villarreal.
At Old Trafford, Bruno Fernandes opened the scoring for United in the ninth minute but Lorenzo Pellegrino levelled with a penalty before Edin Dzeko put Roma ahead in the 34th.
Cavani, however, struck in the 48th and 64th minutes to tilt the tie United's way before a Fernandes penalty in the 71st added to their advantage.
Further strikes from Paul Pogba in the 75th and substitute Mason Greenwood in the 86th ensured a big win for United.
The result leaves 2017 champions United well-placed for next Thursday's second leg in Roma and a place in the May 26 final in Gdansk.
Mikel Arteta's Arsenal went down in Spain in a game where both sides ended with 10 men.
The hosts led 2-0 with goals from Manu Trugeuros and captain Raul Albiol before Nicolas Pepe gave Arsenal a lifeline with a 57th-minute penalty.
It was some degree of revenge for manager Unai Emery who had a miserable and unsuccessful stint with the Gunners at Emirates Stadium.