AA switched from 24-hour hold to 24-hour cancel/refund last year. Flights must be purchased at least 2 days prior to departure (which exceed DOT rules which only require refunds for flights purchased 7 days or more out)
"You have up to 24 hours from the time of ticket purchase for a refund if you booked at least 2 days prior to departure. The 24-hour refund policy applies to all ticket types, but you have to cancel the trip to get a refund."
https://www.aa.com/i18n/customer-ser...rvice-faqs.jsp
AA has holds--I just put an AA itinerary on 24 hour hold last week. They also offer a longer hold for a fee. (Holds on points reservations are 5 or 7 days.)