Would it be possible for these Russian registered aircraft to have their maintenance carried out down route in say Egypt by a third party maintenance company?
Or even Air Egypt? (Just picking a name out of the hat).
Would Boeing be able to tell that there had been an increase in inventory usage?
Would there be repercussions for the third party, like having their approved maintenance removed?
Leaving aside the question of being paid, it could certainly circumnavigate the sanctions and adding a pallet or two of parts every round trip could keep the aircraft flying almost indefinitely (while stripping parts from the leased aircraft).