A crowd of almost 3,500 watched Falkirk win 2-1 to steal the points and leave AIrdrie floundering at the bottom of the table.
There was an element of good fortune attributed to both Falkirk's goals which came after they were a goal down to a well-taken effort by Diamonds defender Craig Ireland.
The big defender rose to powerfully head an Armstrong corner into the net in the 21st minute.
Falkirk's equaliser came eight minutes later when Gareth Hutchison took advantage of the home side's hesitancy to fire in a shot which struck fellow striker Mark Roberts and squeezed its way past Airdrie goalkeeper Javier Sanchez Broto.
The second half was dominated by the home side with Falkirk retreating in numbers on a number of occassions.
It was against the run of play that Falkirk took the lead in the 66th minute when they worked the ball down the left and Hutchison managed to squeeze the ball into the net from a tight angle.
David Nicholls almost scored a third for the Bairns immediately after but his shot went just wide.
Falkirk defended in depth thereafter, resorting to some heavy tactics in defence of their lead and Greig Denham was red carded close to the final whistle.
The 10 men held out for the remaining seconds to record a rather fortunate win.