"
Iridium is currently developing, and is expected to launch during 2017 and 2018, Iridium NEXT, a second-generation worldwide network of telecommunications satellites, consisting of 66 satellites"
Source:
https://en.wikipedia.org/wiki/Iridiu..._constellation
Aireon is based on Iridium NEXT.
See:
https://aireon.com/services/global-a...-surveillance/