Bradford City established a platform to spring another stunning Capital One Cup shock and reach Wembley with victory over Aston Villa at Valley Parade.
Phil Parkinson's League Two side - 60 places beneath Premier League Villa - made light of that gap on a thunderous night in Yorkshire to establish a crucial advantage in the semi-final first leg.
Nahki Wells gave the home side a first-half advantage as goalkeeper Matt Duke produced a string of outstanding saves to keep Villa, and Christian Benteke, at bay.
The Bantams terrorised Villa in the air throughout and it was no surprise when Rory McArdle doubled their lead with a powerful header 13 minutes from time.
Andreas Weimann looked to have given Paul Lambert's side a crucial lifeline with a scrambled late goal, but in a rip-roaring atmosphere Carl McHugh headed in Gary Jones's corner two minutes from time to make it very much advantage Bradford.
The job is only half done but after disposing of Arsenal in the quarter-final there will be no shortage of confidence in the underdogs as they stand 90 minutes from becoming the first side from the lowest tier to reach the final of this competition since Rochdale in 1962.
It was another defensive nightmare for Villa but they will feel they created enough opportunities to still harbour hopes of reaching Wembley. Their recent form, however, suggests the pressure is all on them.
This was Bradford's night and how they celebrated at the final whistle at the conclusion of an extraordinary game, even though they will be well aware that their toughest task still lies ahead.
Darren Bent's goalscoring performance against former club Ipswich Town in the FA Cup was rewarded with a place on the bench as Lambert entrusted the main attacking responsibilities to the menacing figure of Benteke.
And Villa's Belgian summer signing had four opportunities to give Villa the perfect start inside the opening 15 minutes but was twice denied by the outstanding Duke and headed two other presentable opportunities off target.
Once Bradford's nerves had settled, they made light of the gap between themselves and Villa, taking the lead after 20 minutes.
The visitors failed to clear a corner and when Zavon Hines's shot was blocked, it fell invitingly for Wells to sweep a powerful finish past keeper Shay Given to spark wild scenes of celebration.
Bradford sensed the unease of their rattled top-flight opponents and pushed for a second, Jim Hanson's header being kicked off the line by Fabian Delph when he was left unmarked.
Duke was distinguishing himself at regular intervals in Bradford's goal, keeping his side ahead with a fine block from Gabriel Agbonlahor as half-time approached.
Villa boss Lambert clearly delivered a blunt message to his players at the break and they laid siege to Bradford's goal in the early stages of the second half, only to find Duke once more in wonderfully defiant form.
He frustrated Benteke once more from a diving header, then reacted sharply to block another snap shot from Agbonlahor.
It was Agbonlahor's last contribution of significance as he was replaced by Bent - who should have equalised only to head over from six yards after Duke had failed to hold Charles N'Zogbia's shot.
For all Villa's attacking intent, Bradford's endeavour and enthusiasm made them a constant threat, as they added a second with 13 minutes left. Villa's vulnerability in the air was exposed again as once more they failed to clear a corner, allowing Gary Jones to whip in a cross that was powered home by McArdle.
Hanson then headed against the bar as Villa needed something desperately to raise their spirits for the second leg. Weimann was brave enough to provide it as he beat Duke to a loose ball to bundle home.
Bradford, however, were in no mood to be denied and restored that crucial advantage two minutes from time when another corner proved Villa's undoing, McHugh heading in again from another Jones delivery.