I've been driving Grandma half nuts over the years with my ingrained habit of bolting outta the sack at 0430.
Oh yeah, I'll go back to bed and MAYBE sleep until as late as six, but I finally had to tell her the why:
Spent most of my time at an air training command base (NAS Kingsville Texas to be precise), where my barracks was located a couple hundred feet from the flight line, where usually resided three squadrons worth of jet aircraft and directly across the road from the Crash Crew.
Since Texas gets hot so much of the year, Flight Quarters usually went down shortly after 0400, so all of the 40 or so jet engines would begin to start up then followed in short order by those damn firemen starting up their engines along with every bell, siren and whistle they could lay their hands on.
Took six months after I got off active to be able to get to sleep without a jet engine serenade outside and I still haven't shaken their lousy wakeup call after fifty damn years.
Dam Two hunnert