I went on a recent trip that involved a 9 hour flight. I charged my phone prior to leaving, then turned on "Airplane Mode" and put it in my luggage. Upon arrival, I turned my phone on and got a wonderful message saying that I have less than 15% battery left and I should put it on the charger immediately. Now no radios were on, but I'm assuming there was a rogue application that was hanging on a process. The problem is that I'm not sure which one. Battery usage showed "Android System" as the biggest consumer. After this incident, I rebooted my phone and charged it back up and left it in Airplane Mode. Since there was no CDMA network where I was, I left it like this and the phone lasted three days, using WiFi to browse the web at some Cafes (yes, you can still turn WiFi on in Airplane Mode) and taking about 75 pictures a day (EVO's camera is great; best I've seen in a smartphone). Has anyone else had this happen? Are there any steps to prevent this from happening again, or at the very least find out what is causing the problem? I don't have a ton of third party apps on my phone - most of the stuff is pretty standard, or from well known developers (Google Voice, Maps, Opera, Barcode Scanner, Nimbuzz). I'm very confused about this issue, because the Android platform is supposed to take care of everything and do a good job of garbage cleanup.