  Hard X-ray-emitting ($\delta$-type) symbiotic binaries, which exhibit a
strong hard X-ray excess, have posed a challenge to our understanding of
accretion physics in degenerate dwarfs. RT Cru, which is a member of
$\delta$-type symbiotics, shows stochastic X-ray variability. Timing analyses
of X-ray observations from XMM-Newton and NuSTAR, which we consider here,
indicate hourly fluctuations, in addition to a spectral transition from 2007 to
a harder state in 2012 seen with Suzaku observations. To trace the nature of
X-ray variability, we analyze the multi-mission X-ray data using principal
component analysis (PCA), which determines the spectral components mostly
contributing to the flickering behavior and the hardness transition. The
Chandra HRC-S/LETG and XMM-Newton EPIC-pn data provide the primary PCA
components, which may contain some variable emission features, especially in
the soft excess. Additionally, the absorbing column (first order with 50%),
along with the source continuum (20%), and a third component (9%) - which
likely accounts for thermal emission in the soft band - are the three principal
components found in the Suzaku XIS1 observations. The PCA components of the
NuSTAR data also correspond to the continuum and possibly emission features.
Our findings suggest that the spectral hardness transition between the two
Suzaku observations is mainly due to changes in the absorbing material and
X-ray continuum, while some changes in the thermal plasma emission may result
in flickering-type variations.
