Reigning world champion Nina Kennedy made sure to respect the qualifying round and was rewarded with am armchair ride into the Olympic pole vault final as several other big names crashed out.

Kennedy — who shared top spot on the podium at last year's world titles with American Katie Moon — only needed to vault twice for first-up clearances at 4.40m and 4.55m to book her spot in the gold medal decider on Thursday morning, Australian time.

Moon was among six other vaulters who tied for top spot in qualifying with Kennedy.

"I did what I had to do," the 27-year-old Australian said.

The final on Wednesday night will be a marathon affair involving 20 athletes.

But the notable absentees include reigning world indoor champ Molly Caudery — who crashed out in qualifying without clearing a single height — and fellow Brit Holly Bradshaw.

Heading into Paris, Great Britain laid claim to the reigning bronze medallist and the world indoor champion but, by the end of the qualifying, both were in tears with their Olympic dreams shattered.

Bradshaw, who finished third in Tokyo three years ago with a jump of 4.85m, failed to get over 4.40m and was left crying beside the runway after her third failed attempt.

Teammate Caudrey attempted to comfort her, not knowing that in a few minutes she would be in a very similar spot.

Caudrey cleared 4.80m to win the world indoor championships in March and the 24-year-old was so confident in her first Olympic campaign that she sat out the first two heights at 4.20m and 4.40m. 

But she then failed on all three of her attempts at 4.55m, knocking her out of the competition.

To make matters worse, only 11 of the 30 athletes in qualifying made it over 4.55m and, with 12 needed for the final, officials appeared confused as to what that meant for qualifying.

Ultimately, the nine other competitors who cleared 4.40m without any misses went through to the final as well, meaning Caudrey could progressed if she had not sat out the first two heights in qualifying.

"I'm in shock. I'm so disappointed, and I'm so sorry to everyone back at home who's been so supportive," Caudrey said through tears.

"I don't have any excuses. I felt great, I'm in the best shape of my life, I love a big crowd, I didn't feel overly nervous — I just don't have a reason right now for what just happened.

"That height is a bar I jump day in, day out. There was not one piece of doubt in my mind that I could clear it. Maybe people will say I came in too high, but that's not mine or my coach's opinion.

"I've been jumping 4.80m, 4.90m all year round, that height shouldn't be a problem."

Kennedy, who sat out 4.20m, was asked about her fellow world champion's demise and said it was about respecting the process.

"To win Olympic medals, you have to get there. The build-up and qualifying is the hardest part," she said.

Caudrey said she would try to look at it as a learning experience.

"I believe everything is a lesson, and I will find out in time. It's going to take some time to process," she said.

Earlier, Australian big gun Matt Denny looked every inch an Olympic medallist-in-waiting as he powered into the men's discus final with a minimum of fuss.

Denny's second throw of 66.83m was the second best of the qualifying round behind only world-record holder Mykolas Alekna from Lithuania (67.47m).