MLS (Mythical Landing System)
MLS, a system whose time has come,... and GONE. It is now an utter wast of time, energy, and money to invest in it any farther.
The industry having worked on MLS since the 40s, and personally having helped with the original USAF, FAA, and ICAO MLS efforts in the 60s and 70s, into the 80s, and having authored the original ICAO manual of All-Weather Ops with Derek Helmore (UK CAA) and a long list of other FAA authority criteria for AWO, I can confidently say that FAA did the right thing by finally killing MLS dead. Now that needs to happen in Europe too.
The future of NAV globally is in RNP and GBAS/GLS. Not MLS.