A "flyer program" refers to a rewards or loyalty program offered by airlines. It allows frequent flyers to earn points or miles that can be redeemed for free flights, upgrades, or other travel benefits. Full definition
Marriott Rewards members requesting a Mileage Reward must be a member of the relevant airline frequent flyer program in order to receive a Mileage Reward. (flyertalk.com)
With some exceptions, hotels will usually send 1 mile per dollar spent to your frequent flyer program of choice. (pointsmilesandmore.com)
The best part of their airline transfer program is that it automatically adds a 5,000 - mile bonus to your select participating frequent flyer program for every 20,000 points transferred. (upgradedpoints.com)