Originally Posted by EWR764

Under US-EU Open Skies, UA would be permitted to carry pax from the EU (not just CDG) to PPT over SFO.

The complicating factor, as it is with the existing CDG-LAX-PPT flights, is that transit pax must clear US customs on the intermediate stop, despite CDG-PPT being technically a domestic route. Geography is such that there really are no other, more favorable routing options.