Do you know about the Frequent Flyer Program of United Airlines? Well, MileagePlus is the Frequent Flyer Program of this airline and By Subscribing this Program you can earn more miles for your next vacations with United. United has a MileagePlus frequent flyer program. There is one important thing to mention about the program. If you don’t use your points within 18 months you will lose them unless you have a MileagePlus credit card, then they will not expire.