Turn in your resignation on the day you meet with the boss. Hopefully, it will be two weeks prior to starting your new life.
Be humble and calm when meeting with your soon to be ex employer. Be sorry for missing the urgent calls from the 135 coordinator. If you were "on call", you should have answered the phone or called back within 15 minutes maximum.
You "resigned" from this job a few months ago but now will be making it official.
Have fun at the new job. The change will be refreshing.