If you haven’t heard from a social media friend already, United Airlines really wants you to share its newest promotion (see screen shot above).

The airline today launched a three-day promotion for Mileage Plus members that gives a bonus of 35% up to 100% on award miles – if enough people participate. You must buy the miles for yourself or others between by Thursday, Sept. 4.

“The maximum bonus available is based on the number of MileagePlus members worldwide who participate – the more members who buy miles, the greater everyone’s bonus can climb,” United’s statement says.

Visit to buy the miles and to read terms and conditions. There, you can also share the promotion through social media channels and view the progress of the bonus. United promises 100% if there are more than 4,500 qualifying transactions.

As of 12:31 EST, 151 people have participated, according to United’s promo website.