On Friday, European planemaker Airbus posted a photo to Twitter accompanied by the words "This is not just another #A321neo. Can you guess what's so special with this aircraft?" The aircraft photographed was an A321neo and was MSN 10000 - representing a significant milestone for Airbus. The jet was painted in the livery of MEA - the carrier of Lebanon - and is ultimately destined for its new home in Beirut.

So what does MSN actually mean?

MSN stands for Manufacturer Serial Number, which is a somewhat self-explanatory term. It's a unique number assigned to the aircraft used for reference and tracking. According to Vistair, MSNs are used for almost everything, including:

  • Engineering
  • Maintenance
  • Repair
  • Scheduled maintenance
  • Flight operations manuals
  • Data and software

The website also notes that far before MSNs came close to the 10,000-mark, line numbers were only limited to four digits, and a fair amount of work was required to upgrade Airbus information systems and management software to accommodate the extra digit. Presumably, it's a good problem to be faced with!

Boeing and Airbus do things differently

We do need to note, however, that when it comes to Airbus' way of doing things, there is a caveat to the term 'unique.' For the European manufacturer, the number is unique to the family of aircraft.

Thus, an A380 and A320 can both have identical MSNs (below you'll see A380 MSN1 and further down is the A320 with MSN1).

Additionally, sources indicate that if the aircraft is subsequently not built (read: an order cancelation), Airbus will not re-use or reallocate the number.

As far as we understand, Boeing, on the other hand, uses its MSNs slightly differently. An MSN is unique across all aircraft built by the American planemaker. Whether it's a 787 or 707, the number will be unique.

Line numbers for Boeing are somewhat similar to how Airbus uses its MSNs. The line number is unique within the family of aircraft. Unlike Airbus, Boeing resets the line number when the family of aircraft gets a significant update and is classified as another series. Thus, there can be a Boeing 737 from the Classic series and a 737 from the Next Generation (NG) series with the same line number.

How is MSN different from aircraft registration?

Referencing our article explaining aircraft registrations, these codes aren't fixed to the aircraft and will change as the airplane moves from one country to another. This is because the multi-letter code indicates the country or region of registration with the prefix. Anything that is "D-" is registered in Germany while anything "F-" is French. Any registration beginning with N is registered in the United States.

In contrast, an aircraft's MSN will remain with it for the rest of its 'life.'

first A320 msn1
In case you were wondering, this is MSN1 of the Airbus A320 family. Photo: Ken Fielding via Wikimedia Commons 

10,000 is a significant milestone for the A320 family of aircraft. Indeed, this group of aircraft only recently overtook its main competitor - the Boeing 737 family of aircraft - for overall orders across all generations. Congratulations to Airbus on the big achievement!

What do you think of Airbus achieving this significant milestone? Let us know your thoughts in the comments.