  Measurement of the redshifted 21-cm signal of neutral hydrogen from the
Cosmic Dawn (CD) and Epoch of Reionisation (EoR) promises to unveil a wealth of
information about the astrophysical processes during the first billion years of
evolution of the universe. The AARTFAAC Cosmic Explorer (ACE) utilises the
AARTFAAC wide-field imager of LOFAR to measure the power spectrum of the
intensity fluctuations of the redshifted 21-cm signal from the CD at z~18. The
RFI from various sources contaminates the observed data and it is crucial to
exclude the RFI-affected data in the analysis for reliable detection. In this
work, we investigate the impact of non-ground-based transient RFI using
cross-power spectra and cross-coherence metrics to assess the correlation of
RFI over time and investigate the level of impact of transient RFI on the ACE
21-cm power spectrum estimation. We detected moving sky-based transient RFI
sources that cross the field of view within a few minutes and appear to be
mainly from aeroplane communication beacons at the location of the LOFAR core
in the 72-75 MHz band, by inspecting filtered images. This transient RFI is
mostly uncorrelated over time and is only expected to dominate over the thermal
noise for an extremely deep integration time of 3000 hours or more with a
hypothetical instrument that is sky temperature dominated at 75 MHz. We find no
visible correlation over different k-modes in Fourier space in the presence of
noise for realistic thermal noise scenarios. We conclude that the sky-based
transient RFI from aeroplanes, satellites and meteorites at present does not
pose a significant concern for the ACE analyses at the current level of
sensitivity and after integrating over the available 500 hours of observed
data. However, it is crucial to mitigate or filter such transient RFI for more
sensitive experiments aiming for significantly deeper integration.
