  We present various instability mechanisms in the accreting black hole systems
which might indicate at the connection between the accretion disk and jet. The
jets observed in microquasars can have a persistent or blobby morphology.
Correlated with the accretion luminosity, this might provide a link to the
cyclic outbursts of the disk. Such duty-cycle type of behavior on short
timescales results from the thermal instability caused by the radiation
pressure domination. The same type of instability may explain the cyclic
radioactivity of the supermassive black hole systems. The somewhat longer
timescales are characteristic for the instability caused by the partial
hydrogen ionization. The distortions of the jet direction and complex
morphology of the sources can be caused by precession of the disk-jet axis.
