As a Marriott platinum member, are there any benefits/upgrades/disounts for international airline travel?
Not that I am aware of. The only connection is for low-level status with United (from Marriott) and Delta (via Starwood Crossover).
In addition to jbritt51, you can redeem your MR points for travel packages (airline points + 5/7 night stays).
RewardPlus (United) travel packages are pretty popular/valuable in the Marriott system.
Flight and Hotel Packages | Marriott Hotel Packages
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