<quote name="Legoktm" date="2015-05-28" time="10:17:19 -0700">
This means that if we/users spot a bug once the train hits Wikipedias, or the bug is in an extension like PageTriage which is only used on the English Wikipedia, we have to: rush to make the 4pm SWAT window, deploy on Friday, or wait until Monday; which from what I remember were similar reasons from when we moved the train from Thursday to Wednesday.
Emergency bug fixes are already OK on Fridays (just not "I want my new feature out").