That's 2 hours at 600 km/h. A flight would take longer, because of security check, getting to-from airport, waiting for luggage, etc. Also, being on a plane sucks, in my personal opinion. If a train ride was 6 hours, and a plane ride 4, I'd take the train. If it were ~8 and 4, that's where I'd start considering taking a plane.
I'd love overnight trains to come back to Europe.