While there might be something to the underlying tech the current two most promising paths to carbon neutral airlines are synthetic fuel generated with green energy and better batteries. It's highly unlikely that exotic, barely developed hydrogen tech that's not even made it to the "tech demonstrator prototype" phase is going to work exactly the way they're hoping in the end. A few % here and there from unexpected circumstances tends to make a big difference in viability, especially in situations where engineering margins or economic margins are thin (both apply to commercial flight).