Judges in the Dutch city of The Hague will decide on the appeal on October 24.
The appeal has apparently been filed by the air hostess herself, backed up by the airline
The airline's lawyers are also filing a legal challenge against the man directly, and they are said to be particularly unhappy that he has been sharing his wife's email correspondence with third parties believed to include other staff.
It was not specified what emails the man had obtained or who he had been sending them to.
Local media pointed out that not only the reputation of the air hostess, but also the reputation of multiple other staff, apparently many of them married pilots as well as the airline itself, are at stake.
The Dutch airline has also told employees to remain silent if contacted by the media about the story.
A Transavia spokeswoman said: "We take everything very seriously. An internal research has shown that the safety of passengers was never in doubt.
"Our colleagues consider those emails as unwanted and unacceptable as they harm our interests."
The biggest Dutch daily, Telegraaf, which first reported the sex scandal, has reportedly seen internal emails between Transavia and the Dutch airline inspection authority.
The emails allegedly show that the authority is not interested in commenting on the matter, and refers to it as an internal problem for Transavia. The newspaper reported that people with knowledge about the matter speak about a big cover-up behind the scenes.
The spokeswoman said: "It is important in our personnel policy that we take care of our employees. We have talked to everybody, but for now we will not make any comments on that."