A S7 Sibir Airlines Embraer ERJ-170, registration VQ-BYA performing flight S7-1247 from Moscow Domodedovo to Belgorod (Russia), was climbing out of Domodedovo's runway 32L when the crew stopped the climb at about FL180 due to problems retracting the flaps. The aircraft descended to FL150 and entered a hold for about 20 minutes, then returned to Domodedovo for a safe landing on runway 32L about 55 minutes after departure.