In general, one could say that batteries fail way more often than combustion does. It’s not reliable enough yet.
And since engine loss is a catastrophic failure, I don’t see commercial planes being fueled by batteries anytime soon, it would require multiple (to eliminate single-point failures) very reliable batteries, carrying at least 30% excess energy.
And what I mentioned above is not even the biggest problem, it all comes down to the Energy/Weight ratio (very light single-engine electric aircrafts are viable in the next 10 years, I would say).
The power of a jet engine is measured in thrust (lbs, kN). A cruising Boeing 747 requires 55,145 lb (245 295 N) of thrust. This relates to 87,325 hp or 65,000 kW. At take off, the plane produces full thrust at 219,000lb (973 kN) with a power requirement of 105 000 hp or 78,300kW Battery power.
Fully loaded at 400 tons, the Boeing 747 would require 90 mega-watts (MW) of energy to get airborne. This relates to 120,000 horsepower (hp). The energy consumption during cruising is reduced to almost half.
With current technology (11lbs/kW), a battery powerful enough to put fully loaded 747 airborne (90 MW) would weight 992,000lbs/per flight hour (at TO/GA) and 496,000lbs/per flight hour (cruise power).
Thus, an 12-hour flight on a 747 would require approximately 7,500,000lbs worth of batteries (with 2h fuel reserve), this is the equivalent weight of 16 sixteen empty Boeing 747-800s.
Maybe the 2050 Norwegian goal is too optimistic, unless asteroid mining can revolutionize our energy production/storage capabilities somehow in the next 20 years.
I wouldn’t fly, no no, I’m 27y old, maybe my great-grandchildren.