Flore Arrighi, head of the UNAC flight crews' union, said: "It is not our role to pass judgment on the wearing of headscarves or veils in Iran.
What we are denouncing is that it is being made compulsory. Stewardesses must be given the right to refuse these flights."
She added that female staff were entitled to exercise their "individual freedoms".
However, a company spokesman pointed out that other airline staff are obliged to comply with Iranian rules and that "tolerance and respect for the customs of the countries we serve are part of the values of our company".
In Saudi Arabia, stewardesses must wear the "abaya", a long robe that covers the body but, unlike Saudi women, are not compelled to wear face veils.