Since the aerospace/aeronautical sector is so dependent on technical expertise as a driver and indicator of individual excellence, most companies do not advertise what software products they are using for any given task. It's a competitive advantage to hold that information close. However, there are KM-specific organizations that have been able to shed some light on a few companies.
This blog from APQC is an interview with Boeing: https://www.apqc.org/blog/why-boeing-focused-behaviors-not-tools-when-building-its-km-strategy
I know that NASA has several homegrown systems being used across the entire agency and many are supported with taxonomy structures specific to each lab or division.
This thesis for a MS in Aerospace Engineering has some references that you might find useful: https://fenix.tecnico.ulisboa.pt/downloadFile/395145969119/resumo%20alargado.pdf
Some of the top companies you might also search for are United Technologies, Lockheed Martin, General Dynamics, Northrop Grumman, Raytheon, and L3 Communications.
Finally, I think you will find that very few companies are using one single software system for all of their KM needs. More than likely they are using a combination of tools that work effectively together to form a "system."
Dani, you may want to have a look at www.skybrary.aero of EUROCONTROL. It is esssentially an aviation safety encyclopedia built with (semantic) mediawiki. You can find some system key facts via: http://www.skybrary.aero/index.php/Special:Statistics
I am more familiar with KM and KBE concepts that are being used in Aeronautics Industries for product Design and Development. Here are few papers/ application examples. Take a look.
Article Total value management - A knowledge management concept for ...
Conference Paper A Knowledge-Based System Engineering Process for Obtaining E...
Conference Paper When & Where to Use Knowledgeware, Generative Scripts & VB Tools
Technical Report Effective Use of Knowledgeware for Managing Model Size and I...