TV: Watch Stenhousemuir against Falkirk on Sunday on the BBC Scotland channel, as well as Sportscene highlights BBC One Scotland on Saturday (22:25).

Radio: Live BBC Radio Scotland match commentary from Dunfermline Athletic v Kelty Hearts (15:00) and Celtic v Dundee (17:30) on Saturday, along with Rangers v Queen's Park (14:00) on Sunday.

Online: Follow live text coverage of every tie on the BBC Sport website and app, plus watch all the best bits on the BBC iPlayer.

Right, let's take a look at the games tomorrow. Remember, Aberdeen v Motherwell has already been called off due to a waterlogged pitch.

There's been no sunshine in Aberdeen for the last two weeks, according to the Met Office. Anyway, back to the football...

• Dundee United v The Spartans
• Dunfermline Athletic v Kelty Hearts
• Elgin City v Partick Thistle
• Celtic v Dundee (17:30)
• Rangers v Queen's Park (Sunday, 14:00)
• Stenhousemuir v Falkirk (Sunday, 19:30)

St Mirren manager Stephen Robinson tells BBC Scotland: "You're on a hiding to nothing but we found a way. We weren't on top of our game. There's a lot of tired legs from Tuesday night.

"We got better when the subs came on but we lacked quality in the final third. It's a great chance [to get to Hampden]. If you've won a Cup, got to a quarter final, and can stay in the league, it ends up being a terrific season.

"The boys looked tired tonight. The boys we've brought in haven't played a lot of football. I'm asking the same players to go again. Having a few players back will make a huge difference.

"Airdrie were excellent, credit to them. We got really casual after going 1-0 up. Tired minds, poor decisions. They had spells in the game with momentum and it's a lesson."

Image source, SNS

Match-winner Roland Idowu tells BBC Scotland: "It was a tough game. We made it a bit hard for ourselves with sloppy mistakes.

"We ground out a result against a team like this - who play good football, and were good on the day - and we got the result. That's all that matters.

"It was all about momentum. The Hearts game was a good turning point as a squad and we wanted to continue the momentum tonight. We got the win, so it's still a bit of a streak.

"It came to me and I just thought hit it because it sat perfectly."

Image source, SNS

James McFadden
Former Scotland forward on BBC Scotland

Airdrie put a lot in the game and they didn't have as much control in the periods of extra time.

You felt St Mirren were always going to be dangerous. Even when they're not at their best they show great character.

It's all about moments in these games. You need people to step up and thats what they managed to do.

Callum Davidson
Former St Johnstone manager on BBC Scotland

All credit to Airdrie, they made a real game of it. Second half they performed really well and to a man, they were brilliant.

Credit to St Mirren, it's how you progress and they fought. Robbo changed formation, got the wingers on and provided more pressure.

They were the better team in extra-time.

So it was decided in extra-time after all.

Roland Idowu is the match winner, but he looks gutted after missing that late chance. He's the man of the match, so we should hear from him shortly.

Reaction to come.

St Mirren are the first team in the hat for the quarter-final draw.

That's despite the best efforts of a stubborn Airdrie side who gave as good as they got throughout. A fine footballing team, who surely won't toil down the bottom of the Championship for too much longer?

As for St Mirren, it's another Cup run and it follows a battling victory over Hearts. Have they turned the corner?

They won't really care. They'll only care that they're in the next round, and one win away from another Hampden trip.

Image source, SNS

It's St Mirren who break up the other end and Roland Idowu is clear through.

He's got a long time to think about it... and Harry Stone makes the save! That should have been the game but the tiniest lifeline given to Airdrieonians now.

Two minutes of added on time at the Excelsior.

Not sure I'd rule out an equaliser at this stage. The ball is up the right end of the pitch...

Airdrie make the change. Cole McKinnon is off, with Jake Hastie on.

Remember him! Two minutes to make an impact.

A decent whipped ball in there from Liam Donnelly that picks out Roland Idowu at the back post.

His header isn't the best but the replay shows Adam Devine gave him a wee nudge there. Surprised Idowu didn't make more of it.

Liam Donnelly is now coming on to replace Killian Phillips, who just cramped up in midfield. The last roll of the dice for St Mirren, as Stephen Robinson makes his sixth sub of the night.

Early chance for St Mirren's Jalmaro Calvin at the back-post!

The cross from Roland Idowu on the left picked out Calvin, but he didn't get enough on it. A massive let-off for Airdrie.

Right, the final 15 minutes of the game before we potentially go to penalties.

Will there be a moment of magic, or madness, to decide this game?

And so comes to an end an uneventful first-half of extra-time.

I'd love to get the stats and see how many games that go to extra-time are actually decided in extra-time, before going to penalties.

Bring back golden goal, I say! Okay, that didn't work either... but still.

Stephen Craigan
Former Motherwell captain on BBC Scotland

It looks like a weary game, now.

Both sides have exerted a lot of energy. A lot of players played during the week.

It's now mind over body. Make sure you're in the zone.

A caution for dissent for the Irishman.

He's cut a frustrated figure all evening.

Malik Dijksteel, brought on at the start of extra-time, is now coming off. He tried to kick the ball with his left foot and hurt something.

Jalmaro Calvin, the Jamaican winger who hasn't played since October, comes on.