One can alter one's flight date through American Airlines Flight Change, irrespective of the fact whether the ticket was reserved online or offline. Before changing flight dates one must have fool-proof knowledge about that particular airline's policies. One has to make sure one alters the flight date within 24 hours of its booking, that too, only if one's ticket is eligible for the same. There's no extra compensation required if the ticket is cancelled within the above-mentioned period. You're completely exempted from it. However, American Airlines Flight Change charges a flight change fee, of 200$ onwards which varies with the type of ticket booked. In case, the flight date or flight time is shifted or suspended due to any reason by American Airlines itself, then the customers don't have to pay any cost for changing their flight dates.
A few basic rules need to be observed here. As per the authority, the air group follows a 'same day' rule which states that the departure day of the new flights must be on the same calendar day as the original flights booked by a passenger.
Many times, passengers miss flights due to late check-in or traffic, but as per the clauses of American Airlines Flight Change policy, that's not an issue! Flights can be rescheduled to the next vacant day and time. Passengers are permitted to re-schedule their flight 15 minutes before it departs, failing which, is deemed to be the same condition. If one enters the airport on time and still misses the flight or if someone reaches the airport up to 2 hours after the flight's departure, then one is allowed to board another available flight that very day by American Airlines without any extra costs.