the ao dai is now a standard for weddings, for celebrating tết and for other formal occasions. it's the required uniform for female teachers (mostly from high school to below) and female students in common high schools in the south; there is no requirement for color or pattern for teachers while students use plain white with some small patterns like flowers for school uniform. companies often require their female staff to wear uniforms that include the ao dai, so flight attendants, receptionists, bank female staff, restaurant staff, and hotel workers in vietnam may be seen wearing it.