Many years ago (~ 80's) I missed a CO flt while sitting in at the gate. Got engaged in reading material and went into a world of my own. This was before the emphasis of being on board early. When I noticed I was getting close, I was lulled into thinking I had more time due to an erroneous airport clock which was off by 10 mins. Next thing I knew the jet has pushed and the GAs were telling me the miss was my fault. I whined about the bad clock. They took pity and I was on the next available, with no xtra fees, etc. All my bad, but never repeated....