It only has to guarantee the fare for 24 hours - if the airline provided the 24 hours and then the fare expired and is no longer available for puchase, I cannot see DOT doing anything
Also, when holding a reservation, the AA hold policy at
https://www.aa.com/i18n/plan-travel/...eservation.jsp states
Originally Posted by AA
24 hour hold
When available on select American marketed and operated flights, you can hold your reservation up to 24 hours for free if you book seven or more days prior to departure.
Here’s how:
■Choose your flights and select “hold” on the “Review and Pay” page
■Refer to your confirmation email or visit “My Trips” to pay for your trip
■Your reservation will automatically cancel after 24 hours if you don't complete the purchase
Can have inventory held with airlines for weeks - it doesn't guarantee that the fare will not change