Short answer: It depends on your fare and how you exceed it. FitsAir’s free checked allowance varies by fare (20–40 kg); if you go over, the airline charges either a per‑piece fee (USD 50) or an excess‑weight rate (USD 15/kg at the airport). See details below with sources.

Key points (FitsAir official info):

• Free checked allowance by fare:

  • Economy‑Promo: 1 piece (total 20 kg). (FitsAir.com)
  • Economy‑Basic: no checked baggage included. (FitsAir.com)
  • Economy‑Classic: 1 piece (total 30 kg). (FitsAir.com)
  • Economy‑Flex: 2 pieces (total 40 kg). (FitsAir.com)
  • Business: 2 pieces (total 40 kg) per FitsAir announcements. (FitsAir.com)

• Fees if you exceed your allowance:

  • Extra piece (at check‑in): USD 50 per additional piece. (FitsAir.com)
  • Excess weight at the airport (checked baggage over allowance): USD 15 per kg (excluding taxes) charged at the counter. (FitsAir.com)

• Pre‑purchase / other rates (note: FitsAir FAQ lists alternate pre‑purchase/airport rates):

  • FAQ states you can pre‑buy extra 15 kg at city office for USD 90 per 15 kg, or pay USD 10 per kg at the airport when purchased there. (This differs from the USD 15/kg figure above — check your booking or contact FitsAir for the applicable rate for your booking/route.) (FitsAir.com)

• Oversize/other special item charges: e.g., oversized item handling USD 50; TVs and large items have separate fixed fees. (FitsAir.com)

Recommendation: Because allowances and fees can depend on fare class, route and whether you pre‑purchase baggage, I recommend checking your booking confirmation or the FitsAir baggage page (or contacting FitsAir) for the exact baggage allowance and applicable fees on your itinerary. Relevant FitsAir pages: Baggage and FAQs. (FitsAir.com)