Set your air fryer to 375°F (about 190°C) and let it run for 5 minutes. A hot basket starts cooking the beans the moment they land. This small step gives you better browning and a faster cook.
Rinse the beans under cool water and snap off the tough stem ends. Look through them and toss out any that are soft, spotted, or woody. Fresh, good-quality beans make a big difference in the final taste.
Spread the beans on a clean towel and pat them completely dry. Extra water stops them from roasting and leaves them soft and limp. I never skip this step because it is the key to crispy air fryer green beans.
Add the beans to a large bowl with the olive oil, garlic powder, onion powder, smoked paprika, salt, and pepper. Toss them with your hands until every bean is lightly coated. Hands work best here because you can feel the even coating.
Lightly spray the air fryer basket with cooking spray. Add the beans in a single, loose layer so air can move around them. If your basket is small, cook in two or three batches.
Air fry the beans for 8 to 9 minutes total. Pull out the basket halfway through and give it a good shake to flip them. Cook until they are tender with a few browned, blistered spots.
Tip the beans into a serving dish while they are still hot. Taste one and add a pinch more salt if needed. They are at their crispiest in the first few minutes after cooking.