United MileagePlus members can earn up to 15,000 bonus miles for roundtrip nonstop travel between San Francisco and Chengdu from June 9, 2014 through Aug. 31, 2014. The promotion bonus is based on roundtrip nonstop flights operated by United or United Express, but members who only fly one-way will earn half of the listed bonus miles. The amount of bonus miles you will receive is based on fare class and there is no limit to the number of bonuses you can earn during the promotion period. MileagePlus members will earn 5,000 bonus miles for discounted economy E, U, H, Q, V, W, S, T, L, K, G, N fare classes, 10,000 bonus miles for economy Y, B, M fare classes and 15,000 bonus miles for BusinessFirst J, C, D, Z, P fare classes. Members must first register for the promotion at http://insideflyerus.wpengine.com/link/?11336 and travel must be completed by Aug. 31, 2014.