The point in a journey where you have
officially left your starting point and begun traveling to your destination. Your bags are loaded, your kids are strapped in, your fully gassed up, food is packed, and you can officially announce your ETA. For people who run late all the time, this communicates that you have completed
procrastinating and are done going back inside to grab “
one more thing”. It comes from aviation jargon where your wheels leave the runway and you can fold up the landing gear.