Appears that you can get a full refund if you cancel within 24 hours only if you booked 7 days in advance
UNITED STATES OF AMERICA
DEPARTMENT OF TRANSPORTATION
OFFICE OF THE SECRETARY
WASHINGTON, DC
GUIDANCE ON THE 24-HOUR RESERVATION REQUIREMENT
NOTICE
This notice provides guidance to U.S. and foreign air carriers regarding compliance with the
customer service rule that requires carriers to hold a reservation at the quoted fare for 24 hours
without payment or allow a reservation to be cancelled within 24 hours without penalty (the “24-
hour reservation requirement”). The 24-hour reservation requirement is mandated by the
Department of Transportation’s consumer rule “Enhancing Airline Passenger Protections” (14
CFR 259.5(b)(4), 76 Fed. Reg. 23110, 23166, Apr. 25, 2011) and applies to all reservations
made seven days or more prior to the flight’s scheduled departure time.1
In addition it appears some airlines like US airways do not grant full refunds for award flights even if you cancel within 24 hours?
24-hour refund rule
You're allowed to cancel your refundable or non-refundable ticket for a full refund (and no change fees and/or difference in fare) within 24 hours of booking.
Rules:
You must call 800-428-4322 (800-245-2966 TTY) within 24 hours of purchase to cancel the reservation and request a refund.
The reservation must have been booked at least 7 days before scheduled departure.
This policy does not apply to Dividend Miles award tickets.
Refunds are only issued for tickets booked on usairways.com or with US Airways Reservations.