I start by peeling both sweet potatoes and trimming off the ends. Then I cut them into even sticks, about a quarter inch thick, since thinner pieces crisp up faster and more evenly. Keeping the sizes consistent really matters here, because uneven pieces cook at different speeds and you'll end up with some soft and some overdone.
I add the sliced potatoes to a large bowl and sprinkle the cornstarch over them first, tossing well before adding any oil. This little step is what makes sweet potato fries air fryer cornstarch coatings so effective at creating extra crunch. Once they're lightly dusted, I drizzle in the olive oil and toss again until every piece looks coated.
Next, I sprinkle on the salt, garlic powder, smoked paprika, and black pepper directly into the bowl. I use my hands to toss everything together so the spices reach every fry, not just the ones on top. This step takes maybe thirty seconds but makes a big difference in flavor.
I spread the fries out in a single layer in the basket, making sure none of them overlap. This is the sweet potato fries air fryer temperature and spacing combination that actually determines whether they crisp or steam, so I never skip it. If my batch is too big, I just cook it in two rounds.
I set my air fryer to 380°F and cook the fries for about 14 minutes, shaking the basket halfway through. This answers the common question of how long to cook sweet potato fries in air fryer models, though I always keep an eye on the last few minutes since every machine runs a little differently.
Once they're golden and crisp on the edges, I pull them out right away and serve them hot. Sweet potato fries lose some of their crunch the longer they sit, so I like to plate them as soon as the timer goes off.