It's up to you
Occasion: Perfect as Formal Party Dress, Prom Dress, Evening Dress, Gala Dress, Cocktail Party Dress, Bridesmaid Dress, Mother of the Bride Dress, Suit For Black Tie, Dinner, Pageant, Holiday,Ceremony, Quinceanera, Debutante Ball, Anniversary, Semi Formal, Thanksgiving Day, Special Occasion, Birthday Party and Wedding
A long dress is the safe default for a black-tie event and reads unmistakably correct, but a dressy maxi or full-length evening dress in evening fabric works just as well
From Amazon stuff, to various brands at Nordstrom, to LOFT, to that lovely reddish floral dress from Anthropologie last fall (I could not get over how much you were selling that to me, though I didnt end up buying it, using some mega will power) some of these I wouldnt (or havent) taken a second look at on the model but then I see them on you and I love them
Gowns (now restricted to formal occasions) were often extravagantly trimmed and decorated with lace, ribbons, and netting
Some airlines will allow you to carry your gown onboard in a garment bag and hang it in the wardrobe at the front of the plane