Wearing the hijab is a legal requirement for women in Iran. But a controversial Facebook campaign is calling on female tourists visiting the country to post pictures of themselves removing the garment.

The campaign is the work of My Stealthy Freedom, an online movement which is no stranger to this particular act of defiance. Almost two years ago BBC Trending reported on the group's launch, since then the campaign has posted dozens of photos of Iranian women risking arrest by going out in public without the religious head covering.

But its latest request comes in response to the plight of a group of female crew members at a French airline.

When it was announced that Air France would begin flying into Tehran after an eight year hiatus, a number of the female crew demanded the right to opt-out of working on the new route. Why? Well many objected to an internal memo asking them to wear a hijab when disembarking the plane in the Iranian capital.

The crew members have now won the battle. On Monday Air France announced it would allow its female staff to be reassigned to other flights, should they not wish to fly to Iran.