[flavor8]

We don't have a solution for flying without oil based fuels (yet). We might get there, but it makes sense to try to develop much faster ground based transportation in parallel. If they efficiently can hit 600mph without risk of obstruction on the tracks, it becomes a contender. Money will become available to develop the infrastructure if flying becomes prohibitively expensive due to carbon offsets and/or dwindling reserves. As a 25-50 year plan it's fine.