I have got my new iPhone 4S for about two weeks. I noticed several times that the battery went down about 20% overnight (around 8 hours) while it was in the airplane mode. This happened either when the battery was fully charged or when it was partially full. This also happened even when I made sure that the only app that was running in the background was an alarm app while the phone was in the airplane mode. Why did the phone use so much battery while it was in the airplane mode with only an alarm app running in the background? Thanks in advance for answers!