SM said "I now introduce liquid sodium borohydride. This awesome storage medium for hydrogen has been demonstrated by Millennium Cell. It is a liquid at room temperature and pressure, stores 66 percent as much hydrogen per litre as liquid hydrogen, has the same mass-density as water, can be pumped into and out of a tank, and can be re-charged with hydrogen over and over again. The spent fuel is composed of borax in water, and the water can be evaporated away leaving a powder similar to laundry detergent. This means the aircraft does not have to carry spent fuel as excess weight."

OK, let's analyse that. NABH stores 66% of the energy per litre as liquid hydrogen and weighs the same as water.

1 kg of liquid Hydrogen has ~2.5 times the energy content of 1 kg of kerosine, but approx 4 times the volume.

(Actually 2.63 and 1/0.28) Data sources: http://www-formal.stanford.edu/jmc/progress/hydrogen.html and http://www.astronautix.com/props/loxlh2.htm

So 1 litre of liquid hydrogen has only 74% the energy content of kerosine.

NABH is only 66% as good, so has a mere 49% the energy content per litre (and less per kg, because gasoline is less dense than water).

Essentially, NABH is twice as dense as kerosine AND requires evaporation of residual liquid and carriage of a residual powder, but let's ignore those latter points and just look at the energy/kg

Now, let's take a Jumbo Jet. I recently flew across the Pacific and the pilot was kind enough to supply some data. Take-off weight was 390 tonnes, of which ~206 tonnes was fuel. Consumption for the journey was estimated at ~150 tonnes, leaving an ample safety margin. As extra data, passengers and baggage weigh ~ 70 tonnes so the dry airframe is ~ 115 tonnes

Now, let's replace the kerosine with NABH. Fuel consumption = 300 tonnes

Dry airframe + 1 pilot + fuel = 415 tonnes. This exceeds the Max takeoff weight and has no safety margin for fuel, so trans-Pacific flights are out. You would have trouble making Honololu from either side, and the Atlantic would be a major step requiring refuelling in NYC.

Basically, NABH WON'T WORK as aircraft fuel

So unless you are prepared to step back 20 years and cross the world in 3 or 4 hops, we're stuck with hydrocarbon fuel.

No, wait...

I've got another idea. We'll build a super-giant Mumbo Jumbo that will be more efficient because it's bigger. It'll be 10 times the size of a 747, and use safe non-flammable NABH fuel, and still be able to cross the Pacific.

And if one crashes into a tower it can't kill 5,000 people on the ground because there's no fire.

Instead, it kills 5,000 passengers at a time, every time there's an accident...

Reductio Ad Absurdum.