Possible New United Airlines Paint Scheme

Here in the States, they're synonymous. You may see some aircraft with numbering schemes in different spots (UALs is on the nose gear door), but most of the airlines I've seen use some portion of the tail/reg to create this value. UAL's N78001 has the nose number 0001 (the leading 0 indicates it's an ex-COA bird, with the 001 as the trailing three from the tail number). It is registered in the FAA registry as having a registration of N77019. The FAA requires this registration to be placed on any FAA-registered aircraft in a conspicuous location, using all kinds of requirements - size, spacing, proportion, thickness, etc - and this usually ends up near the tail, which is where it comes from. The tail number you're referring to is more of a 'fin' number, which is usually akin to the nose number in concept. DLH, as an example has reg/tail D-AIKE with KE on both the fin and nose.

I can only assume then that the makers of PFPX are making reference to the fin number in the aircraft database, and should consider renaming that field to save confusion. It would seem superfluous to have a "Registration" field and "Tail Number" field per aircraft.

I've also got the lists of 'fin numbers' for other airlines now