The Aviation is a classic gin-based cocktail that is shaken and served straight-up. It is basically a Gin Sour but with lemon juice sourness balanced by...
Like some commenters below, I prefer a well-hued Aviation cocktail, but shaking the creme de Violette makes the color all but disappear. I have tried two approaches that generate the right appearance without substantively changing the cocktail. 1) Add the creme de violette to the chilled serving glass and pour the shaken ingredients over the top. 2) Add the creme de violette to the shaker *after* shaking the other ingredients and stir very briefly, then strain into the serving glass.
There is also Takumi's Aviation that use Parfait Armour (more available than creme violette) and is listed on Difford's. I use a butterfly pea gin (such as Ink Gin) to make a deep purple version of Takumi's Aviation: beautiful.
I confess that I bought a bottle of creme de violette in order to see what an aviation tastes like. I used a standard recipe which I see a lot, and I was not fond of the result (too much violet). I played with it and eventually came up with this: 60 ml gin, 15 ml maraschino liqueur, 3.75 ml creme de violette, and 15 ml lime juice (not lemon). I used Aviation gin, and a different gin might require changes to the recipe.
The Aviation is one that is really hard to get in a color other than muddy gray by the traditional recipe. I wanted one with that light purple/blue hue, which would be a much more attractive cocktail to enjoy without being overly floral. I use 2 oz gin, 1/2 oz clarified lemon juice (just pass through a coffee filter), 1/4 oz creme de violette and 1/4 oz maraschino. Then I STIR over ice and strain. The result is as clear as the sky should be for a good day of flying!
The violet liqueur matters. Where I live there are basically 2 choices for the violet liqueur - Bitter Truth Violet Liqueur and Rothman & Winters Creme de Violette. Bitter Truth makes a beautiful, clear, pale blue dink while R&W makes a muddy purplish gray cocktail. They taste different too - I prefer the Bitter Truth for taste as well as looks in this drink. Also, fine straining the lemon makes the drink more clear.