The secret is cook in oil by 2 steps::
1st time: Oil blanching
Cook at 275 F (135 C) for 5 mins.
2nd time: Crispy cooking
Cook at 350 F (176C) for 5 to 6 mins till brown and crispy.
If you observe in McDonald’s there are two separate oil cooking boilers, and the staff transfer the French fries from one boiler to another boiler for the same reason above.
With Air Frier, you might want to do it in 2 steps similarly.
For Fresh Cut Potatoes:
How to Use the Philips Viva Digital Air Fryer
The temperature she uses is 350 F (or 180 C) for 5 mins, then 390 F (or 200C) for 15 mins.