买了票没有飞的情况很好办，UA网站注册会员然后在自己行程中加入预定号或票号即可绑定。实在不行，提前值机或柜台值机都可以填入会员号。
如果是飞了以后再注册的会员，也可以回溯里程，但需要走申请credit 流程，稍麻烦一点。新会员可以免费申请追回入会前30天内已乘坐的UA航班里程；如果是超过30天的但仍在6个月以内，需要$50的手续费才能申请到。
New MileagePlus members may request mileage and Premier qualifying credit (where applicable) for flights completed on United and United Express up to 30 days prior to their enrollment date. For a $50 USD fee, new members may request mileage credit for flights more than 30 days and up to six months prior to their enrollment date. Contact the MileagePlus Service Center to process this request.
