Those mods included
The logistics center finished a depot-level modification to the F-35A’s fuel system, alleviating an overpressure condition during elevated G-maneuvers
After waiting an answer dudes
Heh! HEH! HEH! Nitrogen Inerting system displaces the O2 in the fuel system with gaseous Nitrogen which suppresses spark ignition, in other words with the nitrogen filling the void between fuel and tank, there is no way you can come up with an "explosive mixture". In addition the pressure relief valve, bleeds off excessive fuel system pressure from high Gs, so as the pressure builds to a certain point the valve releases that inert gas overboard.
My brother had his C-150 fueled to the top Tuesday, before heading home, as the airplane sat on the ramp, the fuel heated up and began to drip out of the overflow. Avgas is a very light fuel, and the vapors are "highly combustible".
JP-4 or whatever they burn these days is much less so, but the vapors will definitely ignite. If you watched the movie "always", when John Goodmans PBY has an engine fire, Richard Dreyfus saves his butt by "bombing" him with slurry, when in the ensuing pull out, Richard Dreyfus sucks a few burning embers into his left engine, the A-26 very shortly thereafter explodes. B-29s were pretty famous for engine fires, but those hot gases are very combustible.
I believe if I recall the F-35 had an engine fire because a compressor blade problem and chafing, anyway, the F-35 uses fuel to cool the avionics or something, a little weird, but much simpler than carrying some type of coolant. KOOOL HUH?
