Reason is that hydrogen burns cleaner than jet fuel. The H2 burns in atmospheric oxygen and the result is just plain water, H2O. Whereas jet fuel, a hydrocarbon, burns down to CO2 and H2O. The greenies love the idea of no C2O in the exhaust of jet liners. Not mentioned is the source of all that hydrogen. In real life, we get hydrogen by reforming natural gas, of which the frackers have given us a good supply. Natural gas is a mixture of various hydrocarbons, methane CH4 being common. There are a lot of other compounds in the natural gas, and reforming squeezes hydrogen out of the ones that have a bit more hydrogen than the methane. So, to fuel up a single jetliner we need maybe 30,000 gallons of hydrogen, and makes that gives us another 30,000 gallons of reformed natural gas. We may have squeezed all the excess hydrogen out of it, but it will still burn just fine. So every gallon of hydrogen burned in flight, we burn another gallon of natural gas on the ground somewhere. This is reducing CO2 in the air?? Never mind, greenies won't understand.
To get enough hydrogen into the aircraft we have to liquefy it. Takes a lot of refrigeration and a lot of pressure to get it liquid. The aircraft's hydrogen tanks have to be very strong and round. The standard aircraft practice of just filling up the wings with liquid fuel won't work, the wings cannot take the pressure. Aviation Week didn't say much about that.
Every so often Aviation Week pushes something really crazy. This year it is hydrogen. Years ago they ran a cover story about a secret American single stage to orbit space plane that was actually flying. That story ran in just that one issue and was never heard of again.