American and Alaska have suspended partnership benefits with Russia's S7 Airlines, which is a fellow Oneworld Alliance member.
Both carriers have also suspended their interline relationship with Russia's largest airline, Aeroflot.
More on the Ukraine crisis
"We are deeply concerned by the humanitarian crisis taking place in Ukraine," Alaska said as it made the announcement Tuesday.
Until further notice, Alaska customers will not be able to earn Mileage Plan miles on S7. The carrier has also halted its work to enable Mileage Plan reward redemptions on S7 flights.
American also suspended its frequent flyer partnership with S7, as well as interline agreements with S7 and Aeroflot. The company notified staff of the moves in its internal Jetwire newsletter on Monday.