Main base is Darwin.
Head office is Darwin, the main base is Alice Springs - there is a difference - Alice was where most of their work and maintenance was done. Aircraft were, in my experience, well maintained and worked hard (2 of their C210s' were the highest time 210s' in the world).
There were some issues there but that was nearly 4 years ago so who knows now? T & Cs' were in accordance with the GA Award, as is the legal minimum in the NT.
DropYourSocks, Directair are much the same as Chartair but smaller. Their head office is Essendon, their main base in the NT is Darwin where most of their NT work is done. They advertise an Alice Springs base but when I was last there it was another company operating under Directair's AOC. That may have long since changed.