Heat an air fryer to 375°F. Meanwhile, trim the stem end from 1 pound green beans and pat dry. Transfer to a large bowl. Add 1 tablespoon olive oil, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper, and toss to combine.
Air fry in batches if needed: Add the green beans to the air fryer basket and arrange into a single layer. Air fry until the green beans are crisp-tender, about 8 minutes. If you prefer your green beans a little more tender, give the basket a toss to redistribute the beans, then cook for 2 minutes more.