The visitors took the lead towards the end of the first half through Fitzgerald, but within minutes Aylesbury were level. Steve Clark powered a header home from an inswinging corner.
The Ducks were under severe pressure for large periods after the break and it was no real surprise when Fitzgerald restored his side's lead.
And then just when it looked like United would never get back into the game Dwain Clarke broke free on the left flank. His pinpoint cross was met by a diving Dwight Marshall who glanced his header past the Northwood keeper.
Clarke had a similar opportunity soon afterwards, but in the heat of the moment decided to shoot from an exceptionally tight angle, when a cross looked to be the better option.
Overall this was United's least consistent ninety minutes of the season to that point. And just when most of the crowd would have settled for a point, Chris Bangura broke through and neatly stroked the ball home to make it three and move his side to the top of the table.