Dinamo Zagreb are right on track to make a first return to the Champions League group stage since 2016-17 following their 2-0 first-leg play-off win over Rosenborg.
Bruno Petkovic put them ahead in the eighth minute from the penalty spot and then 20 minutes later Mislav Orvic doubled the lead.
Barring any capitulation in Norway next week, the Croatian side will return to the European's elite competition after two seasons away.
Red Star Belgrade's hopes of a return to the group stage hang in the balance after a draw at Young Boys.
The Serbian side, who beat champions Liverpool 2-0 in last season's pool stage, saw a lead cancelled out late on to draw 2-2.
Roger Assale gave the Swiss side a perfect start in just the seventh minute before Milos Degenek and Garcia Ezequiel turned it around for Red Star.
But Guillaume Hoarau's penalty levelled for Young Boys, meaning it is all to play for in next week's second leg in the Serbian capital.
Olympiacos got the job done in their home leg as they beat Russian side Krasnodar 4-0.
Miguel Angel Guerrero, Lazar Randelovic (two) and Daniel Podence put the Greek side on the brink of the group stage after a year spent in the Europa League.