Muirhead had given Gus MacPherson's side the advantage in stoppage time of the first leg and the former Kilmarnock, Dundee United and Hearts forward put them further in command in the 12th minute.

Airdrie could not clear a long ball and Muirhead teed himself up to volley into the roof of the net from 25 yards.

Morton were giving their visitors no time on the ball and Cameron Blues missed a good chance to double the lead.

The Greenock side did increase their advantage in the 44th minute, though, when Oliver nodded home from close range after Lewis Strapp had fired off the bar following a well-worked move.

Morton defender Markus Fjortoft mis-kicked from a good chance and Airdrie struggled to get back in the game with two Sean Crighton headers coming from too far out to trouble Scott Fox.

The tie looked beyond the Diamonds before Muirhead knocked the ball into an empty net in the 78th minute after Max Currie could only palm Stephen McGinn's effort straight into his path.

Substitute Aidan Nesbitt missed two good chances to add to Morton's lead as Airdrie's promotion push ended in disappointment.