You would normally be in breach of the airlines terms and conditions.
If you look here
https://www.aa.com/i18n/customer-ser...f-carriage.jsp
It states under Ticket Validity
"Prohibited booking practices
Reservations made to exploit or circumvent fare and ticket rules are prohibited.
Examples include (but are not limited to):
- Purchasing a ticket without intending to fly all flights to gain lower fares (hidden city ticketing)
- Buying a ticket without intending to travel, including to gain access to our airport lounges or other facilities
- Combining 2 or more roundtrip excursion fares end-to-end to circumvent minimum stay requirements (back-to-back ticketing)
- Booking a ticket in someone's name without the person's consent (which is illegal)
- Holding reservations for reasons like securing upgrades, blocking seats or obtaining lower fares
- Booking duplicate or impossible trips, for example multiple trips for the same passenger around the same time (trips a passenger physically could not complete)
If we find evidence that you or your agent are using a prohibited practice, we reserve the right to:
- Cancel any unused part of the ticket
- Refuse to let the passenger fly and check bags
- Not refund an otherwise refundable ticket
- Charge you for what the ticket would have cost if you hadn't booked it fraudulently
- Require you refund to us any compensation we provided like bag delivery costs, and reimbursement for clothes or toiletries because of late or lost bags"
Also search this forum for "Hidden City Ticketing" for likely penalties