  We have used the Far Ultraviolet Spectroscopic Explorer (FUSE) to conduct a
snap-shot survey of O VI variability in the winds of 66 OB-type stars in the
Galaxy and the Magellanic Clouds. These time series consist of two or three
observations separated by intervals ranging from a few days to several months.
Although these time series provide the bare minimum of information required to
detect variations, this survey demonstrates that the O VI doublet in the winds
of OB-type stars is variable on various scales both in time and velocity. For
spectral types from O3 to B1, 64% vary in time. At spectral types later than
B1, no wind variability is observed. This fraction represents a lower limit on
the true incidence of variability in the O VI wind lines, which is very common
and probably ubiquitous. The observed variations extend over several hundreds
of km/s of the wind profile and can be strong. The width over which the wind O
VI profile varies is only weakly correlated with the terminal velocity (\vinf),
but a significant correlation (close to a 1:1 relationship) is derived between
the maximum velocity of the variation and \vinf. High velocity O VI wind
absorption features (possibly related to the discrete absorption components
seen in other wind lines) are also observed in 46% of the cases for spectral
types from O3 to B0.5. These features are variable, but the nature of their
propagation cannot be determined from this survey. If X-rays can produce
sufficient O VI by Auger ionization of O VI, and the X-rays originate from
strong shocks in the wind, this study suggests that stronger shocks occur more
frequently near \vinf, causing an enhancement of O VI near \vinf.
