Manager Neil Lennon says he could never have imagined Celtic would be 12 points clear in the Scottish Premiership title race as early as February.
The champions recovered from the loss of an early goal to beat Kilmarnock 3-1 on the same day that Rangers dropped points in a 2-2 draw at St Johnstone.
In December, Celtic were just two points clear of Rangers after losing the Old Firm derby at Celtic Park.
"It's great for us to extend it [the lead]," Lennon told BBC Scotland.
"It's the icing on the cake, if you want to call it that, but it was just important to keep the momentum today."
Eamonn Brophy had put Kilmarnock ahead from the penalty spot, but Kristoffer Ajer and Odsonne Edouard had Celtic ahead before the break.
Following Alan Power's dismissal for a second yellow card, Leigh Griffiths added a third on what turned out to be a comfortable afternoon for the home side.
"I thought we were outstanding today, considering we went a goal down," said Lennon.
"I'm not happy with the goal [Kilmarnock's], I thought Eamonn was offside once he's got the other side of Jozo [Simunovic]. But our reaction to that was fantastic and it was just a magnificent performance.
"There was a real controlled aggression about us, creativity and hunger, and we should have won the game by more."