After a scruffy opening five minutes, Falkirk took control of the game and started to play through Airdrie with relative ease.
The forward trio of Declan McManus, David McMillan and Lous Longridge were causing real problems for Airdriee defence while Morgaro Gomis was pulling the strings in midfield.
Despte their domination of possession, McKinnon’s side failed to really test David Hutton in the Airdrie goal with Paul Dixon’s long-range effort their best chance.
The visitors hit a sucker punch midway through the first half and took the lead very much against the run of play when Paul McKay out-jumped the otherwise impressive Michael Doyle to head home and leave Robbie Mutch helpless.
It was Airdrie’s first real chance of the game but they made it count and it knocked the wind right out of Falkirk’s sails.
With the crowd now on their back, Falkirk were really struggling to get back into their stride and Airdrie suddenly started to look a bit more dangerous before the referee brought the opening 45 to a close.
The Bairns started the second half on the front foot and it looked as though whatever was said at half-time had got through to them.
McKinnon’s side pushed forward and created a number of chances without making Hutton work.
The equaliser eventually came through McManus as the striker fired home Gregor Buchanan’s header to deservedly draw the Bairns level before a breathtaking save from Mutch denied the Diamonds.
There was late drama to come though as former Rangers kid Calum Gallagher headed home an injury-time corner to send the travelling fans wild.
As the Airdrie fans celebrated, the Falkirk fans were turning on their own manager with abuse raining down from the stands.
Airdrie boss Ian Murray was delighted with his side’s performance and hailed the Diamonds support as they climbed to within a point of the League One summit, saying: “Fantastic result for us so we’re happy to come here and get the three points. It was a really hardworking performance and we had to dig in at times against a dangerous side.
“Overall, as an away team, I thought we played very well and possibly shaded it. Falkirk are a good team but they are having a bit of a tough time at home, a bit like ourselves.
“We used everything in our armoury today, like the long throw-in. I know Falkirk don’t like it because they moaned about it last time after the game. Delighted to score from it and it’s not our problem. They have to defend it. We’ve let in a corner so we’re disappointed with that but I thought the boys were fantastic.”
Falkirk manager Ray McKinnon was furious after seeing his side blow the chance to consolidate their place at the top of the table, calling the defeat “criminal” and admitting losing was “unprofessional.”
“I’m in disbelief. We should have been able to win that game,” McKinnon said.
To lose it was just criminal. It’s unprofessional to lose that game when we are pushing for a winner. To lose it with the last kick of the ball makes it even worse so we’re all feeling a bit deflated at the moment.