We present a large-scale statistical study of the solar wind prop- agnation delay between NASA’s Advanced Composition Explorer spacecraft and ESA’s Cluster 1 spacecraft. This study focuses on those periods when Cluster was within the unimpeded solar wind, upstream of the bow shock nose, between 2001 and 2010. Using a cross-correlation method to compare the ACE and Cluster data, nearly 5000 propagation delays have been calculated and compared to both corresponding propagation delays in the OMNIweb dataset and to those computed by a simple “flat” (i.e. distance/speed) propagation model. The results show that statistically there is little difference between the OMNI and flat propagation delay times and that the cross-correlation method agrees well with both, but there are times when the various methods give significantly different propagation estimates. There is found to be no influence on the relationship between the estimated and observed solar wind propagation delays from the solar wind speed or IMF orientation.