Preheat the air fryer to 200°C (390°F) to get it hot and ready for cooking.
Place the trimmed green beans in a large mixing bowl.
Drizzle the olive oil over the beans and toss well to evenly coat all the green beans.
Add salt, black pepper, and garlic powder (if using), then toss again to distribute the seasonings evenly.
Spread the seasoned green beans in a single layer in the air fryer basket, making sure they aren’t overcrowded so air can circulate freely.
Cook the green beans for 8–10 minutes, shaking the basket halfway through to promote even crisping and browning.
Check the beans—they should be bright green with slightly charred edges and crispy on the outside.
Once cooked, transfer the green beans to a serving dish and sprinkle with a little extra salt or lemon zest if desired.
Serve immediately for the best crispy texture and enjoy this quick, flavorful vegetable side.