I know this is a lot to suggest, but why not make online check-in available 48 hours or more available in advance of flights this weekend. I am flying March 3 and hopefully won't have a problem checking in online and getting my boarding pass. However, the real test will be for those flying Sunday or Monday. It seems it would be a good idea that instead of sending them a warning email, like I just received, that instead an email inviting them to check in now would be a better idea.