比如UA和东航的。
UA里程好像都是可以退的，就是要交手续费？
https://www.united.com/ual/en/us/fly/mileageplus/awards/travel/ticketing.html
但大部分现金机票订了只能转信用点，一年内用完？
In all other cases, a refund may be requested for any fare that allows refunds. Depending on the rules of the fare purchased, a cancellation fee may apply. Most fares are nonrefundable, and are not eligible for voluntary refunds. However, the value of your ticket may be eligible to be applied toward the price of a new ticket for a fee. Tickets are valid one year from the date of ticket issuance, except for tickets purchased between May 1, 2019 and March 31, 2020, which are valid for 24 months.