Antennas don’t fall off...They just don’t fall off. Come up with a different scenario and we can discuss that too. Regards, 23 yrs A&P mechanic DC-9 thru 747.
Apparently there are antennae masts on airplanes.. So calling it a communication mast is not so far off, hmmm. Anyway, maybe they don't fall off, but panels and windows and wheels fall off; I was in Honolulu years back when a 737 landed without a roof, even. But I am not arguing a technical issue but a people issue. Suppose a panel on which an antennae was mounted detached itself from the plane. Technically the antennae did not fall off, but now there is a hole in the structure. Suppose this happened, which it has in the past, and the maintenance personnel had forgotten to turn on the oxygen tanks... This has happened before also. Now you have and accident chain as I mentioned. Without one of these items happening there would not be a missing airliner. People make mistakes is all I am saying, and that is the simplest explanation. Look for the ML370 in the middle of the Indian Ocean.
Your chapter 3 Aircraft Antenna Installation reference is NOT a Boing document, so it doesn’t apply to the 777. Oxygen tanks are turned off and on only for servicing and there is a cockpit indication of oxygen pressure that the pilots verify before departure according to their checklist. These crew oxygen tanks are not accessible from the cockpit.