Brechin won through to the first division play-off final and consigned Airdrie to the second division thanks to a remarkable defensive performance that contrasted with the attacking show in the first leg.
They now play Cowdenbeath on Wednesday and Sunday for a place in the first division.
“It was a different type of game to the first,” said manager Jim Duffy. “We were on the back foot and had our share of luck, but defended well and deployed the counter attack.
“It was a fantastically committed performance to beat a full-time, first division side.”
The counter-attack that brought the only goal was led by Rory McAllister and Charlie King.
McAllister broke clear on a Steve Canning through ball and, with King alongside waiting for the ball to be slipped to him, decided to have a go himself, brushed aside a couple of defenders and fired in a low, fierce shot into the net.
Craig Nelson in the City goal made a string of superb saves but Airdrie will feel aggrieved at a number of refereeing decisions.
The first came after 12 minutes when Scott McLaughlin’s 30-yard strike came off the underside of the bar and appeared to cross the line before it bounced back out.
The second was a netbound volley by Scott Gemmill that struck Steven Canning, with Airdrie claiming it was a blatant handball.DeservedDuffy added, “We won both games and deserve to be going forward, but we had only 14 fit men at the end there.
“Charlie King had to come off with a hamstring injury and he will be assessed on Monday night.
“The games against Cowdenbeath will be tough.”
The two sides are in the same league and have met four times already this season with the advantage swinging in Cowdenbeath’s favour when they beat City 4-0 in the second last game of the normal league programme.
The City showing then and in the following two Airdrie games has club chairman Ken Ferguson hoping his team have saved the best for last.
“Our backs were against the wall at Airdrie and we rode our luck a bit, but we defended well and when the opportunity arose we took it,” he said.
“The players gave everything. It was a fantastic effort over two games. Brechin and Cowdenbeath know each other well and we have a decent chance of going up.”
Duffy added, “The boys have played two games in three days and been at their work in between times. You could see some of them were dead on their feet in the last 10-15 minutes. But they defended unbelievably resolutely.
“Rory McAllister’s been absolutely immense all season. He was a handful all day — not just his goals; his work ethic is magnificent.
“I’m stunned that other people haven’t wanted to buy him. If he keeps the way he’s playing, I’m sure he’ll get a break in the future.”The BBC has announced that both play-off legs will be televised on the Alba channel.