Aircraft Equpiment 'S'??


Check out this tail number:

Look at the aircraft type (PA31/S).

What kind of aircraft equipment is the /S?
It’s not listed on this page: … suffix.rvt

#2 … m0501.html

Table 5-1-2 states the equipment code list, and /S is not on there.

This flight is operated in Canada (outside of the FlightAware service area), possibly it is a Canadian thing. Otherwise, it could simply be a filing error, either it was entered wrong by the pilot or someone at a FSS.


Here is another one which is different since the aircraft changed it’s equipment between flights.


This is an indicator that it is indeed an error. An aircraft wont go from being a /T to a non-existent /S over the course of a single flight. Since these flights are outside of the service area, I predict that it is just not being included in the feed properly.


We’ve noticed the /S (~500 in the last week) and increase in /T where they don’t seem appropriate. We’re working with the FAA to determine and correct the cause.


I surmise that it has to do with the new ICAO (domestic) flight plan filing system.

Under the new ICAO domestic flight plan system (which is only required for those who wish to use RNAV/RNP procedures) the format is completely different. Guidance for those filers can be found HERE. Information from the AOPA regarding the FAA’s En Route Automation Moderization program can be found HERE.

Under the new filing system and suffixes, /S = Transponder - Mode S, including both pressure-altitude and aircraft identification transmission.


We have a winner.