The Bishop of London has said British Airways' (BA) policy on not allowing employees to openly wear a crosses "smacks of religious intolerance".
On Monday, Nadia Eweida, 55, from London, lost her appeal against a decision saying she could not visibly wear her cross at the check-in counter.
The Rt Rev Richard Chartres asked the company to reconsider its decision
BA said it does not discriminate between faiths and said staff could wear such items if concealed.
Ms Eweida said she was effectively "forced" to take unpaid leave after refusing to hide the symbol.
She said people of other faiths were allowed to wear visible religious symbols such as headscarves and she wanted to be allowed to do the same.
BA said Ms Eweida had been offered a non-uniformed post were she would be able to openly wear her cross but had refused to take it.
The Rt Rev Richard Chartres told BBC London: "I think this has turned into a very important and symbolic case and I think she has a right to the British tradition that we should be allowed to express ourselves visibly and in public.
"I'd be very sorry to think she's been forced by a regulation which smacks of religious intolerance.
"If actions like this are permitted to spread then it could very well appear that the historic majority faith is being treated with a greater measure of disrespect than others."
BA said in a statement: "British Airways has 34,000 uniformed staff, all of whom know they must abide by our uniform policy.
"The policy does not ban staff from wearing a cross. It lays down that personal items of jewellery, including crosses may be worn - but underneath the uniform. Other airlines have the same policy.
"The policy recognises that it is not practical for some religious symbols - such as turbans and hijabs - to be worn underneath the uniform. This is purely a question of practicality. There is no discrimination between faiths.
"In Nadia Eweida's case, she is not suspended and we want her to come back to work."
But the Rt Rev Richard Chartres said: " I hope even at this late stage BA can say something more convincing than simply, 'the rules, are the rules, are the rules'.
"BA should change their minds and think again."