Nadia Eweida had taken her case to the European Court of Human Rights (ECHR) in Strasbourg to fight for the right to express her Christian faith.
In a majority judgement, the court ruled that "the domestic authorities failed sufficiently to protect the applicant's right to manifest her religion, in breach of the positive obligation under Article 9 (of the European convention on human rights, which guarantees freedom of thought, conscience and religion)."
The 60-year-old had taken legal action back in 2006 after she was banned from displaying her white gold cross necklace at work and vowed to carry on her fight after she lost an initial appeal in the UK.
BA amended its uniform code in 2007 to allow employees to wear symbols of faith and Eweida, a check-in worker, has continued to work there for 13 years.
Three other Christian applicants