Just a late night random thought.. Instead of multiple codeshare flight numbers for a single flight (eg, UA 852 aka CO 6010 aka NH 7012 aka TG 5604 aka US 6514), why don't they assign single *A identifiers, eg *A 9876 for common use by all *A carriers that codeshare on the flight. Reprogramming systems would presumably be required but it might clear up confusion for travellers and simplify departure boards to boot....