Since I booked my flight 3 months ago, theschedule has change at least 6 times, just by a few minutes, sometimes only the arriving time. However, everytime they change I'll lose my seat assignment, and the ability of selecting seats. Most of the time our seats were not changed in Delta system when I called, but a couple of time me and my two young kids were scattered three different areas. Luckiely I called early enough to get consecutive seats back, just to find they were gone again a week later. I can't think of a reason they do this (without any plane type change) and I'm so tired of calling.