Preheat the air fryer to 400°F (204°C).
If slicing: place the peppers in a large bowl, drizzle with olive oil, season with salt and pepper, and toss to coat evenly.
Arrange peppers in a single layer in the air fryer basket; work in batches if necessary so pieces aren’t crowded.
Air fry at 400°F until peppers are fork-tender with browned edges, about 10–12 minutes for sliced peppers; shake the basket or turn peppers halfway through for even cooking.
If roasting whole peppers to peel: air fry whole peppers at 400°F until skin is charred and blistered, about 10–15 minutes, turning as needed for even charring.
Transfer roasted whole peppers to a bowl and cover tightly with plastic wrap; let sit about 10 minutes until cool enough to handle and the skin loosens.
Use gloves or a towel to rub off and discard the blackened skin; optionally remove stem and seeds, or leave them in for your recipe.