Early bird

Hi gents, In my quest for more realism (and to get plausible flight ideas), I was browsing several airlines's websites. I found out that the 738 is mostly used to do the first flight of the day towards a given destination. It is then usually replaced by smaller 737's, Airbus, ATR or McDonnell's aicrafts for the rest of the day. Here's a list of what I found so far : - Air Algerie (DAAG 7:25 -DAOO 8:35)- Air Austria (LOWW 6:35 - EGLL 8:05)- KLM (EHAM 7:15 - LFPG 8:35) Is there any reason for that? Or is just a coincidence? Regards,