I recently received an email from a reader, Bob S, asking me about aircraft tail numbers. It seemed like a simple topic, but I found myself diving in and learning more than I ever thought I cared to know. It was awesome. The result is a two part series talking about how most carriers in the US pick their registration numbers. Today, we’ll look at the big four US carriers and their subsidiaries. Next time, we’ll look at everyone else.

First, what is a tail number? Every aircraft in the world is registered (possibly excluding some nefarious operations). Just like your car’s license plate, every airplane has a unique identifying combination of letters and numbers which must be displayed on the outside of the airplane. Like a license plate on a car, it can be re-registered during its lifetime. Every country has its own code to begin the tail number. Some, like Canada, which starts with C, makes sense. Others, like the US? Not so much. (Here’s a full list.)

In the US, all tail numbers begin with the letter N. Why? There is actually a pretty fascinating history of the so-called “N Number” that stretches back 100 years. It’s tied to radio call signs and the Navy. Since 1948, all registration numbers in the US have started with N and then been followed by up to 5 additional characters.

With this jumble of numbers and letters, most airlines have opted to give some sort of order to the process. If you know what the order is, then you can glean a fair bit from a registration number alone. But when it comes to the big guys, it gets more complex. A consistent system is tough when you have 1,000 airplanes to register so the biggest carriers have created their own “nose numbers” which are internal designations that are sometimes not tied to the registration number at all. I spoke with Joe Maloy from US Airways (now with American) about how the merger has created some logistical challenges in that regard. Let’s dive in with American first.

American (including US Airways, Envoy, Piedmont, and PSA)



American has some old airplanes, and because of that, it has a lot of different registration formats that have been used over the years. Now with the merger, the airline is trying to create a standard nose number system and then tie the tail numbers as closely as possible going forward (but that will be tough). Thanks to inflexible technology systems, those nose numbers have to have 3 characters (no more, no less). The plan going forward is to have the Boeing aircraft start with a fleet number and then be followed by two characters. The 737-800 above is 3KS (as you can see in small type), for example. The Airbus fleet will also be three characters but it will be all digits. The first A319, for example, is 001 where 0 is the A319 fleet number for American’s deliveries. This helps explain why American’s pre-merger A319 registrations are so goofy.

The first American A319, N8001N seems straightforward. That’s fleet number 0, aircraft number 01. But the second one is N9002U. Then the third one falls off the rails with N93003. Looking at the full list, you can see that they just picked random numbers and letters that would allow them to stuff the nose number in there somewhere. There isn’t much of a pattern. That changes with the other fleets, however.

Please note that the suffix you see on these, sometimes AA or AN, won’t be the same for every airplane. Sometimes, the preferred suffix won’t be available so they use a backup like AM or even just A. And there are always a couple random ones that don’t fit the mold. Also, when you look at the formats, note that x is a number and z is a letter. If you see some overlap, that’s because old fleets (MD-80/757/767) are being phased out in favor of newer ones, so they will start to replace each other.

MD-82/83 N4xxAA (nose number 4xx) N7x4xx (nose number 4xx) N5xxAA (nose number 5xx) Nxx5xx (nose number 5xx) N7x5xx (nose number 5xx) N75xxx (nose number 5xx) N9xxxx (former TWA aircraft) (nose number 4zz)

737-800 N9xxAN first (nose number 3zz) then N8xxNN (nose number 3zz) currently N9xxNN (nose number 3zz)

A321 N1xxNN (nose number 783-799 for A321T, 850-999 for others)

757-200 N6xxAA (nose number 5zz) N1xxAN (nose number 5zz)

767-300 N3xxAA (nose number 3xx) N393xx (nose number 3xx)

777-200 N7xxAN (xx = 50 or higher) (nose number 7zz)

777-300 N7xxAN (xx = 49 or lower) (nose number 7zz)



On the US Airways side, it’s a mix of both America West and US Airways aircraft. You can figure out which are which very easily. If it ends in AW, that means it was an America West airplane originally. The nose numbers match the tail numbers here for the most part, and the numbers you see below are the ones that will exist in the new combined fleet.

Embraer 190 N9xxUW (xx = 43 to 67) (nose number 9xx carved out of AA A321 range)

A319 N7xxUW or US (CFM-powered) (nose number 7xx) N8xxAW (IAE-powered) (nose number 8xx)

A320 N1xxUW or US (CFM-powered) (xx = 102-128) (nose number 1xx) N6xxAW (IAE-powered) (nose number 6xx)

A321 N1xxUW or US (CFM-powered) (xx = 150 and higher) (nose number 1xx) N5xxUW or AY (IAE-powered) (nose number 5xx) N9xxUY (post-American merger IAE-powered) (nose number 9xx)

757-200 N2xxUW (xx = 00 to 07) (nose number 2xx) N9xxUW (xx = 35 to 42) (nose number 9xx) N9xxAW (xx = 01 to 10) (nose number 9xx)

767-200 N2xxAY (xx = 48 to 56) (nose number 2xx)

A330-200/300 N2xxAY (xx = 70 and higher) (nose number 2xx)



There are a few special registrations in the US Airways fleet. When the airline painted retro liveries to honor its predecessor airlines, it went all out and re-registered the airplanes to fit.

N475VJ: Allegheny retro colors (the VJ stands for VistaJet)

N742PS: PSA retro colors

N744P: Piedmont retro colors

American now has three wholly-owned regionals as well.

Envoy

ERJ-140 N8xxAE

ERJ-145 N6xxAE N9xxAE

CRJ-700 N5xxAE



Piedmont

Dash 8-100 N8xxEX (former Allegheny aircraft)

Dash 8-100 N9xxHA (former Henson aircraft)

Dash 8-300 N3xxEN



PSA

CRJ-200 N2xxPS or JS

CRJ-700 N7xxPS

CRJ-900 N5xxNN



You can see that even the regionals have begun adopting American’s scheme. The new CRJ-900 deliveries at PSA fit with American’s registration system.

Delta (including Endeavor)



If you want a maddening exercise, try to figure out how Delta registers its 757 and 767 fleets. There’s such a mish-mash of origins here that it can be tough. But that doesn’t stop me from trying. As always, there can be minor variations here if they can’t get the exact registration they want for each aircraft. The aircraft ending in US and NW are Northwest airplanes. For whatever reason, Northwest previously used US as it suffix. I’ve asked Delta for info on where the NB came from (also ex-Northwest), but I haven’t heard back. [Updated: As mentioned in the comments, NB stands for Norwest Bank, the original owner of the Northwest A319s.) I’ll have a few notes down below.

717-200 N8xxAT N9xxAT (former AirTran aircraft)

A319 N3xxNB (former Northwest aircraft)

737-700 N3xxDQ or DE

MD-80 N9xxDE or DL

MD-90 N9xxDA or DN

A320 N3xxUS (xx = 26 or lower) (former Northwest aircraft) N3xxNW (xx = 27 or higher) (former Northwest aircraft)

737-800 N3xxDA or DN N37xxz

737-900 N8xxDN (xx = 859 and lower)

757-200 N5xxUS (xx = 549 and lower) (former Northwest aircraft) N5xxNW (xx = 550 to 580) (former Northwest aircraft) N6xxDL or DA or DN N67xxx (former Song aircraft) N7xxTW (former TWA aircraft) N7xxAT (former ATA aircraft)

757-300 N5xxNW (xx = 581 and higher) (former Northwest aircraft)

767-300 N1xxDL (xx = 129 to 149)

767-300ER N1xxDL (xx = 150 to 159) (former Gulf Air aircraft) N16xxz N1xxDN (xx = 169 to 199)

767-400 N8xxMH

A330-200/300 N8xxNW (former Northwest aircraft)

777-200ER N8xxDA (xx = 860 and higher)

777-200LR N7xxDN

747-400 N6xxUS



Quite a list, huh? The one thing that stood out for me was the 767-400. Why the heck is there an MH suffix on that? I’m told by someone outside the company that it stands for Mullin Holdings. That’s right, you can thank former CEO Leo Mullin for that little ridiculousness. I haven’t been able to get the airline to confirm that.

As for Delta’s wholly-owned regional, it’s a mish-mash of previously-owned airplanes that haven’t been re-registered.

Endeavor

CRJ-200 N6xxXJ (former Mesaba aircraft) N8xxAY N8xxxz

CRJ-900 N2xxPQ N3xxPQ N6xxLR (former Mesa aircraft) N9xxXJ (former Mesaba aircraft)



Southwest



Southwest by far has the most fun with aircraft registrations. Fortunately, I was able to speak with the airline’s guru on this matter, Richard West. Richard has written about some of this on the Southwest blog, but here’s as complete a list as I could come up with.

The original methodology for registrations was NxxxSW. If SW wasn’t available, they’d use SA (Southwest Airlines), WN (the airline’s two letter code) or LV (for the LoVe airline). A few of the 737-700s have GS at the end. That stands for Gene Stewart, the 737-700 project director for the airline. This standard gave us the following registrations:

737-500 N5xxSW (xx = 49 and lower)

737-300 N3xxSW N6xxSW

737-700 N2xxSW N4xxSW N5xxSW (xx = 50 and higher) N7xxSW N9xxWN



As Southwest continued to grow, the time came to change the standard to use 4 digits and then a single letter at the end in order to have more options. The 737-800 fleet uses this across the board. The AirTran 737-700s and any new 737-700s that come into the fleet will follow this standard as well.

737-700 N77xxz (former AirTran aircraft and new additions)

737-800 N86xxz

737-800 ETOPS N83xxz



With all that being said, Southwest has a ton of special registrations meant to honor various people and groups.

N216WR and N217JC: two employees who were killed in a general aviation crash

N289CT: Charles Taylor, 1st airplane mechanic under the Wright brothers

N500WR: William Rogers, the Southwest representative at Boeing. This was his 500th delivery.

N711HK: Herb Kelleher, former CEO (remains in the original colors)

N714CB: Colleen Barrett, former President (remains in the original colors)

N737JW: Jim Wimberley, former COO

N738CB: Colleen Barrett, former President (again)

N739GB: Gary Barron, former EVP and COO

N761RR: Ron Ricks, EVP

N777QC: Quality Control department, they didn’t have many options on the 777 aircraft, so this stuck

N797MX: Maintenance department, similar story

These guys clearly put a lot of thought into this, and I like it.

United



Talk about a tale of two airlines. Pre-merger United had just about the cleanest system possible for such a big airline. Pre-merger Continental, not so much? Continental went with an N##xxx configuration. What are the pound signs? Those are numbers like the “x,” but spokesperson Rahsaan Johnson confirmed that, with limited exception, those two digits are completely random while the last three are aircraft numbers. Go figure. (If you’re wondering which ones aren’t random, Rahsaan mentioned N77014 where that was meant to tie to the Peter Max 777 it was.)

A319 N8xxUA

737-700 N##7xx (xx = 49 and lower) (former Continental aircraft)

A320 N4xxUA

737-800 N##2xx N##5xx

737-900 N##4xx (xx = 12 and lower)

737-900ER N##4xx (xx = 13 and higher) N##8xx (xx = 50 and lower)

757-200 N##1xx N5xxUA

757-300 N##8xx (xx = 51 and higher)

767-300 N6xxUA

767-400 N##0xx (xx = 51 and higher)

787-8 N##9xx (xx = 949 and lower)

787-9 N–9xx (xx = 950 and higher)

777-200 N7xxUA

N2xxUA

N##0xx (xx = 50 and lower)

747-400 N1xxUA

By far the big four carriers are the ones who make life the most complex. Next time, we’ll look at the smaller legacy carriers, the low cost carriers, and the regionals.