Yes, PFC's (fare code XF) which are typically $4.50 per departure airport (the maximum allowed by US law) are considered non-refundable on non-refundable fares. Note that airports must designate specific airport improvement projects for these fees and get approval from the government for them. They are not allowed to be used for general ongoing airport operations expenses. So for US domestic flights, the only fee that's potentially refundable is the $5.60 (one way) TSA tax (fare code AY).