Impossible, Illogical and Duplicate Bookings
"American Airlines specifically prohibits practices commonly known as: (in part)

"Duplicate and impossible/illogical bookings: Duplicate or impossible/illogical American Airlines bookings are prohibited without prior authorization from American Airlines. A duplicate or impossible/illogical booking includes, but is not limited to, bookings for the same passenger on flights traveling on or about the same date between one or more of the same or nearby origin and/or destination (such as JFK to DFW and LGA to DFW or DFW to LAX and DFW to ONT), or bookings with connections that depart before the arrival of the inbound flight."

Also please note: "Fraudulent, fictitious and abusive bookings: Fraudulent, fictitious and/or abusive bookings are prohibited. These types of bookings are defined as any bookings made without having been requested by or on behalf of the named passenger. Additionally, creating bookings to hold or block seats for the purpose of obtaining lower fares, AAdvantage award inventory, or upgrades that may not otherwise be available, or to gain access to airport facilities, or to circumvent any of American Airlines' fare rules or policies, is prohibited without prior authorization from American Airlines."

Link to AA Conditions of Carriage
Link to Sep 2010 thread announcing AA issuance of rules pertaining to this issue.