Fries/chips can be made at home and the only method specifically prohibited is "deep frying", so it would depend on if the air fryer fits more in the spirit of the program on the side of roasting or the side of frying. Ya, the air fryer does use drastically less oil than a deep fryer, but that's not necessarily the primary since W30 is not fat-phobic after all -- the issue is more the end product result I think. Probably falls more in the FWB category than SWYPO? My vote would be to skip 'em for the 30 days.
Some related discussion here: http://forum.whole30.com/topic/29592-sweet-potato-chips/