These seat covers are compatible with the airbags in the seat. They created a little hidden pocket for the side material to sit under. In the event the airbag is deployed, the airbag would easily push the extra material out of the way.
These were purchased through CoverKing by way of Costco at $199 for the set. They're made out of neoprene like a wetsuit. If I had to guess they're about 4mm thick.
I decide after about 10 days these seat covers aren't for me. So get a set for the front seats of your Leaf for $85! Includes shipping to your doorstep!