Since embarking on their maiden European voyage in the old Inter-City Fairs Cup some 64 years ago, Celtic have scaled some dizzying heights and experienced some crushing lows.

Perhaps never before has the sense of sheer desolation felt quite as acute as it did when the final whistle signal sounded last night in northern Austria.

On an occasion when Martin O'Neill's side simply wilted before your eyes, a return ticket to the big stage was ripped up and the accompanying £40million in prize money slipped through the club's hands.

It was a catastrophic outcome – one which beggared belief after such a commanding display in Glasgow six days previously.

How could a side which was in such complete control of a tie at the midway point look so ramshackle and lost?

It's much too easy to cite complacency on the players' part as the reason why Celtic again crashed out at this stage. They didn't initially play like a team that already believed the job was done. They just stopped playing.

Not since collapsing away to MTK Hungarian in 1963-64 had Celtic surrendered a three-goal first leg lead. The fallout from this will be nuclear.

For all the board were given some credit for lavishing £30million on four players, two of those – Mika Baur and Haissem Hassan – arrived too late in the window to take this match in their stride.

And where are the others which O'Neill evidently needed in the door sooner? The left-back, the holding midfielder that European football demands, the additional creative influence?

A club that's still in profit for this window didn't get its act together in good time. And, accordingly, it won't be returning to the big stage.

And so, the name of LASK joins that of AEK Athens, Cluj, Ferencvaros, Midtjylland, Kairat Almaty as sides to have knocked Celtic out in Champions League qualification in recent times.

You could lose one of those ties, maybe two, even if you are going about things the right way. When you chalk up six losses on the spin, you aren't behaving like a serious football club.

Few who watched this debacle unfold will ever have seen anything like it. It was scarcely believable.

When Callum McGregor found the net in 21 minutes, Celtic were four goals up on aggregate and contemplating what Thursday's draw in Monaco might bring.

While Benjamin Nygren's error allowed Moses Usor to level on the night before the break, there was no need to panic.

But that's exactly what unfolded. Austin Trusty's error played a part in Robert Ljubicic cutting the aggregate deficit to two.

More untidy defending then saw Samuel Adeniran net LASK's third and at that point Celtic were running about with their hair on fire.

With the Austrians completely dominant and managing 31 attempts in regulation time, the only wonder was that it took them until the 90th minute to square the tie with substitute Florian Flecker heading home a rebound.

Adeniran sealed an extraordinary comeback in extra-time following another elementary error and even had the luxury of having a penalty saved.

Celtic actually started the game fairly well. Baur's cross had a little too much on it for Kasper Hogh.

The German's interception sent Hogh in on goal. A poor execution ensured the keeper saved comfortably.

LASK were not shy at trying their luck from distance or shelling the box with crosses.

They were left with their heads in their hands when Xavier Mbuyamba failed to convert at the back post following a flick-on.

O'Neill's heart would have skipped a beat when Melayro Bogarde's strike took a deflection off McGregor and bounced off the upright.

Arriving just before the midway point in the first half, Celtic's opener owed everything to their pace and invention down the left flank.

Hyun-jun Yang played the ball back to Kieran Tierney and darted forward. Having taken the return ball, he bobbed and weaved while assessing his options.

Having correctly identified that McGregor was best placed to capitalise, he cut the ball back. The skipper's left-foot strike came off the outstretched leg of Andres Andrade and beat Lukas Jungwirth in goal.

Hogh looked like removing any lingering doubt soon after only for a nudge in his back to put him off.

With LASK looking increasingly frustrated, Adeniran pulled a shot wide of the far post then left one on Colby Donovan.

Celtic should have been coasting at half-time. Instead, LASK gave them something to worry about.

There was nothing wrong with Cameron Carter-Vickers' pass to Benjamin Nygren. The Swede went blind with his attempted pass back.

Moses Usor could hardly believe his luck. A calm first-time finish gave the Austrians hope.

For O'Neill's players, it was a question of staying disciplined and sticking to their respective tasks at the outset of the second period.

Yet within three minutes, Trusty got himself done for pace and power on the left. LASK moved the ball into the central Robert Ljubicic.

The playmaker's shot from the edge of the box did fly through a thicket of legs. Still, Sinisalo was too easily beaten.

Ten minutes later, the unthinkable inched ever closer. A long punt up the park found Celtic's defence disjointed.

Donovan gave Ljubicic too much space to pick a pass to Adeniran. To that point in the tie, the American had played like his laces had been tied together. Not this time. His cushioned left-foot strike curled away from the outstretched arm of Sinisalo. Celtic were in trouble.

Reo Hatate and Seb Tounekti were introduced before Luke McCowan and Liam Scales joined them. Dane Murray later replaced the stricken Donovan.

Sinisalo did well to turn Sascha Horvath's deflected strike wide then watched Joao Viktor Tornich's point blank header flash wide.

When Adeniran's strike thumped the underside of the bar, the ball hit Sinisalo's back but stayed out. Celtic were riding their luck.

O'Neill picked up a booking for venting his growing frustrations at the officials. Of greater concern was Kasper Jorgensen's shot which flew narrowly wide. Celtic were handing the ball as if it was a hot potato.

The clock had just struck 90 minutes when they conceded again. Finding himself in acres of space on the left, George Bello crossed. Sinisalo did brilliantly to prevent an initial header from finding the net but could do nothing as sub Florian Flecker nodded home the rebound.

All the momentum was with the Austrians in extra-time. Celtic got through the first period only to concede a fifth four minutes after the turnaround.

McCowan became the latest visiting player to make an enforced error when he won the ball on the edge of his own box and had his pocket picked. The ball was worked to Adeniran at the edge of the box who beat Sinisalo all too easily.

The Finn kept Celtic breathing by saving Adeniran's penalty after Hatate had felled Krystof Danek. It only prolonged the agony.