Orbitz: In most cases, Orbitz will allow you to cancel tickets on US carriers, up to 10pm (or sometimes 11 pm) on the day following purchase. However, individual cases may vary and all tickets are governed by the terms and conditions you agreed to when you purchased them. Some fares are non-refundable; if you cancel, you may be eligible for a flight credit instead.
Travelocity: Travelocity allows 24-hour flight cancellation, but there is some fine print. To be eligible for 24-hour flight cancellation by Travelocity you must have booked each ticket you are seeking to cancel on Travelocity.com at least seven days before the scheduled departure date. If your itinerary includes multiple tickets (such as a roundtrip that combines two different airlines), these terms will apply to each ticket separately—there is also a list of airlines for which this rule does not apply, mostly international low-cost carriers.
Expedia: Expedia’s language is a bit cagey. “For some airfares, if you cancel within 24 hours, no penalty fees apply,” which sounds like you can still cancel within 24 hours. However, it also states that “If you cancel a non-refundable flight reservation, the airline may issue you a flight credit for a future booking instead of a refund” and that “some flight reservations are not eligible for a flight credit after cancellation. If you cancel one of these reservations, you will lose the value of your ticket.” Basically, you might be able to cancel within 24 hours if you have the right type of reservation. To be safe, read the fine print when you book.
Priceline: Priceline allows 24 hours to cancel or change your flight without penalty in most cases, but you can actually stretch it to 72 hours in some instances because Priceline actually allows you to cancel many tickets free of charge until 11:29 PM ET the next business day. So if you book on a Friday that means you can cancel the ticket without penalty until 11:29 PM ET on the following Monday. You’ll need to check the exact cancellation terms for your ticket as this policy doesn’t apply to Express Deals or flights on certain airlines such as Frontier and Spirit. If you purchase an “Express Deal,” in which the full itinerary is not disclosed prior to purchase, this fare is non-refundable and non-changeable.