What is the origin of the term “pax”?

Pax in commercial transport is used as something like persons or passengers, in the context of counting people, e.g. 150 pax onboard.

I observed that in German writers tend to use the meaning:

PAX = Persons approximately.
(Source: European Union and the Committee of the Regions)

English.SE has a page for What does “pax” mean in the context of the apartment rental? Selected answer:

Pax isn't exactly shorthand for Passengers. It's short for Passengers and Passes.

But the author of the answer agreed that another answer was likely more accurate. The latter has a reference to a magazine, Air Facts: The Magazine for Pilots - 1946:

Cargo is known as "cargo", but passengers are called "pax" by the traffic department, who puts them on and takes them off the airplane and "bodies" by the crews who fly them.

Pax could be from passenger as usually assumed in the Aviation community, albeit I don't see why not *pass" instead. I wouldn't be surprised it comes from the merchant navy.

Can we track the use further back to the origin in aviation field?

• Might be better asked on english.stackexchange.com where you can inquire about the etymology of certain phrases. I don't think its specific to aviation, pretty much any industry that caters to passengers uses "pax" as an abbreviation, so aviation may just borrow it from an unrelated field. – Ron Beyer Feb 12 '16 at 14:34
• @mins Would be interesting to know if it was in use during the steamship era too e.g. pre 1920. – curious_cat Feb 12 '16 at 14:50
• FYI, I am ex-military (air force) and never heard pax used except to mean passenger. – Simon Feb 12 '16 at 16:09
• @curious_cat I wonder if some of the uses of pax from 1800s and earlier were related to the Latin word meaning 'peace' (e.g. the "Pax Romana") rather than as an abbreviation for 'passengers' as it's used in aviation? – reirab Feb 12 '16 at 16:43
• when I worked in the airline technology business, IATA was the authoritative source of data processing systems. according to IATA, PAX means passenger. you can find lots of references googling 'IATA PAX' – rbp Feb 12 '16 at 17:44

The 'x' suffix is aviation speak in an abbreviated word called a contraction. You can think of the 'x' as "cut short" shorthand. Some are defined in manuals or advisory circulars. For example, WX is weather as defined in an old advisory circular, AC00-45.

Official or not, a few others that come to mind are:

MX - maintenance
CX - cancel
TX - transmit
• Please see the link contraction in my answer, for example. The right-hand column of that government document shows a source. – STWilson Jun 9 '17 at 18:12
• Rx & Tx are common for Receive & Transmit in the computer world, as well - look at your router/modem & you will, most likely see a light for each. – FreeMan Jun 9 '17 at 20:27