Join Date: Mar 2001
Location: Fort Worth TX
Programs: Earned status with AA, DL, SPG, HH, Hyatt, Marriott, Seabourn, NCL, National, Hertz...I miss my bed!
Posts: 10,927
It completely varies by agent, in my experience. If the agent who checks you in for MIA says no, ask another one. Or go out to ticketing before you leave.
I've been told I can't check a bag more than four hours before (that old "we want you WITH your luggage" thing), but they were more than happy to give me a boarding pass.