Air hostesses working for Turkish Airlines are now banned from wearing brightly-colored lipsticks, like red or pink.
The decision sparked a debate on the government Islamizing the country, many saying it is an act of perversion.
Many women posted pictures of themselves wearing red lipstick on social media sites to protest the measure.
It is the most recent in a series of conservative measures implemented by the airline.
But Turkish Airlines is claiming that the new rule has nothing to do with Islamic culture, and is simply reflective of how they want their hostesses to look.
"Simple make-up, immaculate and in pastel colors, is preferred for staff working in the service sector," they said in a statement.
The airline is 49 percent state-owned. It has also recently decided to stop serving alcohol.
Other changes include a proposal of new uniforms for flight attendants, which feature ankle-length dresses and Ottoman-style fez caps. Many criticized the outfits to be too conservative, as the previous uniforms had skirts that hit above the knee.
They have not officially implemented these new uniforms yet.
Though the country mainly consists of Muslims, it is a secular state. Prime Minister Recep Tayyin Erdogan, who has a deeply rooted Islamist Justice and Development Party, has been accused of coercing the country into being more conservative.
Since he has taken the role of Prime Minister, headscarves have become more visible in public places and alcohol bans have become more widespread.