We used to always fly in day of. Guess we were just lucky on all those cruises. Also lucky that we don't usually have to deal with connections when flying from Chicago. However we did have a scary situation when one of the girls in our group missed her flight that changed how we travel going forward.
It's a very interesting story. She got up on time, took a shower, then laid down and fell back asleep. So it was her fault, not the airline, but from then it was just like anything that could go wrong did. Our original flight was actually delayed...and she was standing at the counter talking to us sitting on the plane while the mechanic's were fixing something. But they wouldn't let her thru to board our plane. So they put her on another flight, but didn't tell her it made a stop in Indianapolis. Tell her she's confirmed, but when she gets to Indy they pull her off and tell her she's not confirmed but standby. Finally let her back on that plane. Then gets to Miami and there is some issue with security and there are no cabs! This whole time either me or her were on the phone with Carnival (and they were wonderful by the way!). While waiting on the cab issue, she's told the others waiting that she's trying to make the ship. When a cab shows up, someone who hadn't even been waiting just throws her stuff in the trunk. Luckily everyone else in line knew the story and helped her remove the luggage and get her in the cab. When she got to the terminal, they were literally ready to pull up the gangway. She was such a wreck she couldn't fill out her paperwork (this was back in the days before we filled everything out online) so the shoreside staff filled it out for her. When we got a call on our cabin phone a minute before the boat drill saying she was next door in her cabin, it was a huge relief for all!
To make it even more fun, her roommate that cruise was a last minute name change. She had NO paperwork even showing she was supposed to be on the cruise...just a handwritten receipt from the travel agent for the name change fee. Luckily there we no issues with that part.
So...needless to say, based on that experience we always fly in the day before and also always have travel insurance!