Y'all who miss the pre-9/11 days of airport loitering: Are there any small airports near you? Say, a municipal or metro airport? You still can't go past the commercial gate unless you're ticketed, but there's usually other places to be.
I'm thinking first of the Rocky Mountain Metro Airport in Broomfield, Colorado (formerly known as the Jefferson County Airport, but then Broomfield stopped being part of Jefferson County when Broomfield County was formed). You can drive right up Airport Road, circle the traffic control tower, park at one of the buildings, walk upstairs, and have a meal and a writing session in the Parkway Diner. The view of the runway is fun: little Cessnas and big King Airs take off and land all day long. The other diners are in large part pilots, crew, and student pilots catching a bite before their next flight or studying flight maps with their instructors. Also the tables all have sectional maps under the glass, which are fun to look at.
And then at the Boulder Municipal Airport, in the main FBO, no one will blink at you if you settle down on the couch with a cup of coffee and your computer. They might ask if you're there for a lesson, but if the answer is no, I doubt they'd chase you out. Remember to leave a buck in the community coffee jar, though.
I suppose if I wanted to pay the parking fees I could run off to the Denver International Airport and hang out in the fast food restaurants near ticketing. For inspiration, there's an art gallery on your way to the security gate down the hallway to Concourse A.
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My own favorite places to write: at the big oak desk I've been lugging around with me since college, currently stationed in our spare bedroom; at certain of Boulder's coffee-and-tea shops, with special great love for Pekoe Steelyards, Atlas Purveyors, and Ku Cha House of Tea; sitting up in my freshy-made bed with my computer set up on a cheap Bed Bath & Beyond lap desk. I try to enjoy writing at the library, but something always distracts me there. I think it's the books.