Okay I am going to give you the bad news first and just to let you know how serious this is....what you are doing by intentionally over drafting your account is a form of fraud and in some cases could end you up being arrested.
Your bank account is not a line of credit. When you are attempting to spend money that is not in your account it is 100% up to your bank if they will approve or decline the charge. Whether or not they pay it will most likely depend on how "negative" this puts you as well as your history with them. If this puts you a couple hundred dollars negative and you have a history of doing this they may decline it. If you have only one other negative and this only puts you a few dollars negative it may get approved.
As to if the ticket went through..do you have a confirmation number? This is generally a set of 5-6 Alpha-Numeric characters. If you received this then the odds are you do have a confirmed(and paid for flight) according to the airline, and it would be very rare for them to go through and cancel the ticket.
If you have a Confirmation Number, most likely one of two scenarios will happen.
1) PayPal will request from your bank the amount of the plane ticket. The bank will approve it, put you in the negative with your bank, and fine with PayPal.
2) PayPal will request the money from your bank. The bank will decline it, and you are now in the negative with PayPal but fine with your bank.
Because you bought this on a Weekend and Monday is a Holiday, it may still stay pending and not be until Tuesday until you find out which one happens as banks don't post transactions on Weekends or Holidays. Just realize that in both cases the company you are negative with may not give you the time to put the money back "when you get it". If you wait too long the bank or PayPal could close your account and turn you over to collections for the negative amount.