Originally Posted by Gone Flying

i think this was covered already but per far 121 you need 1000 hours of any of the following
pt.121 SIC
pt. 135 PIC in a plane with 10 or more seats ME ( like another poster requires a ATP by regs to be PIC)
pt. 91K PIC (same as 135)
you can count up to 500 hours of mil PIC in a multi engine, multi crew, fixed wing AC

second thought, SKW is currently not letting FOs switch seats with any regularity. look at all the CRJ FOs in SLC who are not being let onto the 175 as new hires get the base. when you were hired you have a 2 year seat lock and if you switch airplanes that would incur another 1 year seat lock before you can upgrade, assuming they even let you change planes.