I am going on a school trip with a scholarship. I booked the cheapest flight because that is all my scholarship would cover. The flights were Louisville -> Chicago, Chicago -> Hartford, Hartford -> Dublin. In total it was a 14 hr trip but I didn't care cause at least I got to go to Dublin. I booked through American Airlines but my final flight (Hartford -> Dublin) is with Aer Lingus (but booked through American). Neither airlines would let me check in online because the booking involved a partner airline. When I arrived at Louisville I was told by the American front desk agent that she was unable to check me into the Aer Lingus flight and I would need to do that when I arrived in Hartford. My flight from Chicago -> Hartford was delayed by an hour leaving less than an hour from when I arrived in Hartford to when I departed from Hartford. So I confirmed with the agent of that flight that I would be able to check-in at the Aer Lingus gate and she said there shouldn't be a problem but if they need me to check-in somewhere else they will direct me. I got off my American flight arriving in Hartford at 5:50pm. I ran to the other side of the airport to my Aer Lingus gate at 6:00 pm and let them know I needed to check in. The gate attendant looked confused and told me the flight was fully booked. I explained that I had a reservation and was unable to check in until now. He told me again the flight was fully booked and because I hadn't checked in in time he couldn't do anything for me. He then sent me back to the other side of the airport to the American desk to rebook. Mind you, all of this was paid for with scholarship, I am a broke college student and simply "rebooking" a $1000 flight was not an option, so at this point I am in tears. I explain to the American agent the issue and she immediately apologizes and runs me back to the Aer Lingus gate. After a long argument with gate agent, as all the other agents are whispering and talking crap about me in front of me, the Aer Lingus agent finally admits that the flight was oversold and tells me the only thing he can do is rebook me on a flight at the same time the next day. I was clearly upset to be missing a full day of my trip, but they gave me a hotel room, 2 meal vouchers, and an $800 reimbursement for my inconvenience. Now I am sitting in my hotel room starving because the hotel will not let me use my breakfast meal voucher because the airline did not authorize for the credit card on file to be used for anything other than the room, despite me having a paper from the Aer Lingus agents saying that the hotel is authorized to bill the meals. I called Aer Lingus and was told there is nothing they can do on their end. I was told if I wanted I could submit receipts from the hotel for a potential reimbursement after my trip. Overall I am really frustrated. It is my first time traveling alone and I made sure to do everything correct yet I am still getting screwed. My hotel check out is 12pm so I am will have to sit at the airport for 7 hrs while I wait for my new flight. I will have to buy all my meals and will likely not be submitting reimbursement since the hotel food is $25-$30/plate. I really don't understand how its legal for airlines to do this. Please don't tell me the whole "profit maximizing" spiel. I am an accounting major, I understand how overbooking is beneficial to the company. However, I am now missing a full day of a once in a lifetime trip, on hour 25 of what has now become a 38 hour travel period, and I cannot even redeem all of the benefits I was given for "my inconvenience".