United Airlines policies regarding checking strollers, car seats, mobility devices and sports equipment.
Sports Items - Several sports items like archery equipment and fishing equipment count toward the checked-in luggage allowance (thus for some destinations it may cost you what it would cost to check in your first or second piece of luggage, whereas for other international ones it may qualify to be checked in for free).
Heavier/larger equipment, for the most part, may be checked for a cost of $175 - $250 per direction.
Strollers, Car Seats - Transported free of charge.
Mobility Devices - Wheelchairs, scooters, braces, etc. are accepted free of charge as checked baggage and do not count as part of the checked luggage allowance.