Pizza, Fast Food, Burgers, Tacos, more fast food, more pizza, more carbs, more carbs, MOAR CARBS! Pretty much everything at an airport is either booze or carbs... so what's a Keto traveler to do?
I struggle with this literally every airport I'm in. This is a hard one. How do you go low-carb when all they want to do is ram carbs down your throat and charge you five times what it would cost outside the airport? The answer is, reach in and tap your inner hunter and researcher. This is where planning, careful thinking, and some practice come into play.
Look for a real, sit-down, serve you at a table restaurant. This is your most likely bet. More unusual than that, go with a chain you've heard of. They've likely posted their nutritional menu online and with an app like MyFitnessPal you can literally find out the carbs, fiber, protein, and fat present in what you're about to eat.
Now, you've gotta get real comfortable with the fact that while, yes, it'd be great if I could eat everything hormone-free, grass-fed, and given daily massages... this isn't going to be your reality in an airport. IF, and that's a really big if, you can find something that serves this type of food, GO THERE! If, like most airports, you can't, then opt for steak, fish, and/or chicken. A Cobb salad also never hurt anyone, but just keep your macros and calories in mind when looking at the ingredients.
Find a place that will serve you avocado. This tasty, super healthy, and keto-friendly food will take you a long way in reducing your satiety, increasing your fat and fiber intake, and generally just being a super food you can't get enough of on your Keto diet.
News Stands, Quick Stops, Travel Stores
Look, the easiest things you're going to find here are almonds and jerky (be really careful about jerky and use something like Epic Chicken Sriracha. You can also get stocked up on water, but you're going to be limited in these places!
I'll also say Oberto makes a hell of a bacon jerky with next to zero carbs and a very high fat content. That stuff is like heaven in my mouth but it's rare to find but dang... if you do, snag you some of that and eat it like there's no tomorrow.
The Long and Short
Look, the long and short of this is: Pay attention and be mindful of what you're eating. Ask servers questions, read labels, be the weirdo in the airport. Nobody gives a crap what other people think because you're literally never going to see 99.999% of these people again! You come first, your diet goals come first, and hey, if anyone has anything to say, send them here to the Keto Traveler for some education!
Good luck out there and if you need advice, have advice, think I may be full of crap, or hey, if I just missed something... let me know in the comments below!