Arsenal will defend the FA Cup in next month's final after Adam Federici's extra-time error cost Reading this evening's semi-final at Wembley.
The long-serving Royals goalkeeper allowed Alexis Sanchez's 105th-minute shot to squirm through his legs to spare the blushes of his opposite number.
It was a mistake from Wojciech Szczesny which had allowed Garath McCleary to equalise for the Championship side after Sanchez had given the Gunners a half-time lead.
However, the PFA Player of the Year nominee struck again to put Arsenal on course to regain the trophy against either Liverpool or Aston Villa on May 30.
Federici had to be alert to keep out Per Mertesacker's seventh-minute header at his near post, but the Royals held their own for the remainder of the opening 20 minutes.
Although their only threat on the Arsenal goal was Jordan Obita's well-struck half-volley which was saved by Szczesny, they largely stifled an opponent who have won their last eight games in all competitions.
The Premier League giants began to knock on the door as the half went on as Ozil clipped a free kick narrowly wide of the post and Santi Cazorla released Sanchez to poke wide under pressure from several Reading defenders.
Eventually Arsenal's class showed as Ozil picked out Sanchez with a fine pass which the Chilean collected before cleverly evading a couple of challenges in the box to slot beyond Federici on 39 minutes.
Reading refused to lie down and equalised 10 minutes into the second half as Pavel Pogrebnyak stood up a cross to the back post, where McCleary met the ball with a volley which beat Szczesny's weak low save.
Gabriel Paulista, brought on as a substitute for the injured Mertesacker, had two good chances to restore Arsenal's lead, but he nodded off target from close range moments after Federici had tipped his header onto the bar at full stretch.
His miss was nothing compared to that of Aaron Ramsey - Arsenal's hero when they won the competition last year to end a nine-year silverware drought. The Welshman struck the post from six yards on 82 minutes when the goal had been left vacant following Federici's efforts to save his initial shot.
Steve Clarke's side had their own opportunity to clinch victory in normal time when Pogrebnyak and Mackie ran clear in a two-on-one situation, but the latter's hesitance in making a run deterred the Russian and the opening went begging.
It appeared as though Arsenal were heading for another penalty shootout against Championship opposition - as they faced against Wigan Athletic in the last four last season - but Federici's howler at the end of the first additional period saved them that ordeal.
Sanchez cut in from the left and made some room to get away a tame shot which took a slight deflection that may have contributed to the ball slipping through the Australian's legs and over the line, despite his desperate attempts to claw it back.
Olivier Giroud hit the post on 115 minutes as the Gunners tried to ensure that there was not another twist in the tale, but the deflated Royals could not apply any late pressure as Arsene Wenger's men reached a joint-best 18th final.
