Originally Posted by
nycflyer
....There could be one bucket of six digit numbers reserved for common *A use, eg
UA 852 = CO 110852 = NH 110852 = TG 110852 = US 110852 = *A 110852.....
Many GDS and airlines systems can only accommodate 4-digit flight numbers. This will require massive amount of system upgrades across GDS and all airlines worldwide, not just *A as other airlines can interline to *A too. Tickets need to be redesigned too as current ATB only allows 4-digit. Yes, paper tickets still exist in parts of this world. The trouble with changing airlines systems is that it needs to be uniform worldwide for interlining.
It will be simpler to outlaw codeshares.

I think codeshares are one of the biggest scams in the world with few benefits to customers.