Lewis Spence boosted Brechin’s bid to beat the drop with a goal he claimed was the best he’s ever scored.
The on-loan Dunfermline Athletic midfielder lobbed home from 35 yards as the Hedgemen made it three clean-sheet victories in a row.
Andy Jackson had given City, who are now level on points with ninth-placed Forfar Athletic and just two behind Cowdenbeath in eighth, a first-half lead.
Spence stole the show with an audacious effort after the interval to sink Airdrieonians at New Broomfield and boost Brechin’s hopes of survival in League One.
The delighted 20-year-old said: “It’s probably the best goal I have scored in my career. I don’t know how far out I was and I was quite shocked it went in.
“The ball broke to me and I was going to go on a dribble but I saw the keeper off his line. I used the inside of my foot and caught it quite sweet. I don’t think I’ll score a goal like that ever again in my life. It was a really good goal but I needed a wee bit of luck as well.
“We coped with everything they threw at us and the work-rate and togetherness in the team was excellent. That’s what you need when you’re at the bottom of the league.
“We’re right back in it and it’s in our hands. There are plenty of games left and we’ve got a bit of momentum.
“Everybody wrote us off but we’ve managed to claw back those points.”
Jackson brightened up a low-key opening period when he smashed an effort in off the post after the Diamonds got into a muddle defensively.
And it was all over bar the shouting once Spence took aim from distance with the ball bouncing into the net.
The home side were rarely a threat, with City comfortably seeing out the tie.
Brechin player/manager Darren Dods said: “We knew it was going to be tough as we’ve struggled against Airdrie this season.
“But we’ve worked on becoming more solid at the back and we’ve confidence that we can score goals. We’ve got to keep the momentum going.”
Danny Lennon, Airdrie’s acting head coach, said: “I thought we started the game brightly but we lost the first goal at a bad time and it set us back.”