Palace were held to a disappointing 1-1 draw by Bosnian side Zrinjski in the first leg of their play-off tie last week.
But Oliver Glasner’s team avoided an embarrassing exit thanks to goals from Maxence Lacroix and Evann Guessand in the play-off second leg at Selhurst Park.
Playing their first European knock-out tie in the main stage of a tournament, Palace’s 3-1 aggregate victory eased the pressure on the under-fire Glasner.
After a poor recent run in the Premier League and a stunning FA Cup exit against sixth-tier Macclesfield, Glasner, who has confirmed he will leave at the end of the season, had been subjected to chants for his sacking.
Glasner earned some breathing space as Palace struck in the 36th minute when Adam Wharton’s free-kick picked out Lacroix and the defender headed home from close range.
Guessand, who scored Palace’s winner against Wolves last weekend, drilled into the far corner from Brennan Johnson’s pass in stoppage time.
“It means a lot. We didn’t have many easy weeks,” Glasner said.
“I always said, since day number one, we’ve had a great relationship with the fans. Yes, they were a little bit critical but they can be critical when the results and performances are not that well.”
Palace face German outfit Mainz or AEK Larnaca of Cyprus in the last 16.
Meanwhile, Fiorentina were on the verge of humiliation before earning a dramatic 5-4 aggregate victory over Polish team Jagiellonia.
Paolo Vanoli’s side blew their 3-0 first leg lead as Bartosz Mazurek’s hat-trick for Jagiellonia forced extra time at the Artemio Franchi stadium.
Fiorentina finally regained control of the second leg of their play-off tie thanks to Nicolo Fagioli’s strike and Taras Romanchuk’s own goal.
Jesus Imaz’s 118th-minute strike made Fiorentina sweat, but Jagiellonia’s Bernardo Vital was sent off for a second booking in the final seconds of a 4-2 win that wasn’t enough for the Poles.
Currently languishing in 16th place in Serie A, Fiorentina’s main concern is fighting to avoid relegation.
But they have reached two Conference League finals, losing to West Ham and Olympiakos, and one semi-final, in the last three editions.
The Italian club, whose lone European trophy is the 1961 Uefa Cup, remain on course for another deep run.
Dutch club AZ Alkmaar beat Armenian side Noah 4-0, overturning a 1-0 first leg deficit to secure a last 16 clash against Czech side Sparta Prague or Greek club AEK Athens.
Lech Poznan of Poland won 1-0 against Finland’s KuPS, clinching a 3-0 aggregate success, and next face Ukrainian side Shakhtar Donetsk or Spain’s Rayo Vallecano.
Czech outfit Sigma Olomouc won 2-1 at Switzerland’s Lausanne-Sport, giving them a 3-2 aggregate victory and a last 16 showdown against Mainz or AEK Larnaca.
Slovenian league leaders Celje defeated Kosovo’s FC Drita 3-2 to advance 6-4 on aggregate, with Sparta Prague or AEK Athens lying in wait in the last 16.
Croatia club Rijeka beat Cypriot side Omonia Nicosia 3-1 to advance 4-1 on aggregate, setting up a meeting with Strasbourg or Rakow Czestochowa.
Samsunspor routed North Macedonia’s Shkendija 4-0 to seal a 5-0 aggregate victory and will face Shakhtar Donetsk or Rayo Vallecano. (AFP)
Edited by Cecil Wong
