The only problem you might run into is if you get stuck in the airport and have to stay overnight. If you are under 18 they won't arrange accomodations for you, nor will many hotels let you stay. It can be quite a pain in the ass, I've had it happen to me a couple of times (been flying alone since 15). Yeah, I had a 1hour argument once, they were like we can't take responsibility for you so you can sleep by yourself in an cold airport floor where you might get robbed rather than put you in a hotel like we did with everyone else:disgust:
And I always have the bad weather in Chicago, half the time my plane ends up delayed or cancelled.