In 2009, on one of my many many Florida trips with my family, I decided to book us a KEF-BOS-TPA routing with Icelandair/jetBlue with one night in the Hilton at Logan.
We arrived around 8pm in the evening from KEF and went straight to sleep as our flight the next day was scheduled to leave at 5:50. Well, we woke up at 3:30 and were at the jetBlue check-in machines around 4am. We didn't understand what was going on when we entered our booking numbers and the machine said "You can only check-in 5 hours before depature".
Completely confused, we walked over to the manned check-in counter and asked why in the world the machine gave us that message. The agent checked our ticket and suddenly laughed out loud. He then took up a pen and underlined the departure time: 5.50
pm.
In my defense, we use the 24-hr system in Iceland!
It also worked out quite well as I had no plans in Florida that day so we just went into downtown Boston and had a long lunch at the Cheesecake Factory.
As if this is not stupid enough, last spring I did the same thing AGAIN. Booked a US flight DCA-TPA at 7.30, only to notice the pm behind it after getting the e-ticket. Changed to a 9.30am flight, 200$ out the window in change fees.
Regards, Sveinn