rframe
pǝʇɹǝʌuı
Everybody can have a bad day, but if it happens more than once or twice I'm pretty blunt about it... "looks like you have too much other stuff going on, and my schedule is already tight with other students so I have to keep things on track to be fair to everyone, so let me know if anything changes with your schedule where you can fly consistently and on time...". They either straighten up or leave, either way... win!