There is an established "Range" of appropriate attire for an Airline interview. To put it bluntly its not burger king. A doctor or lawyer would not walk into a form and show up wearing khakis and a polo because that is not the well know industry standard. The responsibility and demeanor of this profession has set a standard, and they uphold it, we all uphold it so that both employer and employee realize that this is not burger king.
There are always exceptions; you will here people say they wore an orange tie and blue suit while still getting hired, who knows. All that may be true but is it likely, probably not. It’s ok to stand out but just make sure if you go outside the norm you are personally ok with it and can deal with any additional attention you may get.
Good Luck
If you are interested here is a look at the norm
http://airlinepilotmentor.com/airlineinterviews.aspx