Often a symptom of air in the system, yes. But could also be too much "slack", i.e. freeplay present. Pedal to pushrod hole wear, slave pushrod to clutch linkage play, clutch arm play.
One SURE way to bleed a clutch system(first pop off the boot on the slave and make sure the piston is pushed out towards the rod. If it is in towards the bottom of the cylinder, you will never get it completely bled.) Is to get a pressure bleeder and reverse bleed from the slave cylinder. Also, make sure the bleed port is facing up, the highest part of the slave cylinder.
Something like a mity-vac. Fill the mity vac reservoir with clean brake fluid, then using the pressure port on the mity vac pump(usually at the top of the pump body) hook up a line from the pressure port, to the reservoir, to the bleed port on the slave cylinder, then pump, keeping an eye on the master cylinder so that the fluid does not spill out onto the paint..
Works every time..