The vast majority of international air cargo moves on passenger aircraft, so in reality as long as it will fit through the loading door on the plane you're flying on, you can check it. It of course will cost extra but it can be done.

I've taken, and sent other "hand couriers", with carts full of boxes for several large well known US manufacturers. If a manufacturer must have something the most sure way is to "hand carry" it... I.e. Check it as your baggage and fly with the cargo.