Atletico Madrid and Sporting Lisbon held the balance of power after Thursday's Europa League semi-final first legs.
Atletico, inspired by a Falcao double, beat Valencia 4-2 in Madrid, while a stunning late comeback from Sporting saw them topple Athletic Bilbao 2-1 across the border in the Portuguese capital.
Poor defending by Valencia's Adil Rami was partly to blame for 2010 winners Atletico taking an 18th-minute lead.
Arda Turan cut the ball back off the goal line and after taking a deflection Falcao headed past Diego Alves for his 31st goal of the season and his 11th in the last dozen games.
Against the run of play Valencia went into the break all square after Rami headed the ball down for Jonas to tap in from a corner deep into first half stoppage time.
Atletico were only back on the pitch four minutes before they had regained the advantage with the unmarked Miranda heading in low past Alves off Diego's long range freekick.
Atletico moved even closer to the final in Bucharest in the 54th minute after a charging run by Adrian Lopez who produced a clinical finish with a tight angled shot to foil Alves.
This was the 24-year-old's 10th goal in Europe this season, a fitting way to mark his 50th game for his club.
Falcao then appeared to have wrapped up a memorable night for Atletico, running rings round the Valencia defence to slam the ball into the roof of Alves's net for his 32nd goal of the campaign.
The in-form Colombian striker has fond memories of last year's Europa League final when he scored the winning goal for Porto in Dublin.
But some of the gloss was taken off Atletico's night when Ricardo Costa grabbed a potentially crucial stoppage time goal, a header off a corner, to keep Valencia's hopes of making the May 9 final alive.
The prospect of an all-Spanish final looked very much on the cards nine minutes after the restart in Lisbon.
After a first half stalemate Bilbao grabbed an all important away goal when Jon Aurtenetxe volleyed home a freekick from the right after the ball was flicked on by Sporting's Emiliano Insua.
But Sporting weren't about to capitulate having come this far in the competition.
They went close to getting back on level terms only for Ricky van Wolfswinkel to miss the target with a gilt-edged header from inside the six yard box.
But on 75 minutes former Liverpool back Emiliano Insua did put the hosts back in the game with his header into the corner of Gorka Iraizoz's net.
And five minutes later the Portuguese side completed their comeback when Diego Capel's shot from outside the box whistled past Iraizoz to give Sporting the upper hand ahead of the return leg in Bilbao.
Bilbao forward Oscar de Marcos will miss next Thursday's game after picking up a first half yellow card.