Does anyone know what UAL (or DAL) policy is on seat assignments out of Asia? Form example, if coach is full, will the gate agents leave you at the gate because they won't/can't put you in biz or first?

I've had instances where the comments by the gate agents left me feeling like they will only put you in coach as a matter of policy. I don't recall ever getting biz at the gate coming from Asia. So I'm not sure if they have a policy of coach only for jumpseaters or if they just give you coach before anything if its available.

Any insight?