As for what happens if you firewall the throttles at low altitude in a jet, I'd say flutter is unlikely to be the first problem you encounter. Your TAS will not be all that high after all. The drag caused by the dynamic pressures encountered will limit your acceleration.
However, the same drag due to dynamic pressure and the same forces which limit your acceleration will have an adverse effect on the structure of your aircraft. To put it another way, you may start shedding antennas, windshield wipers, landing gear doors, control surfaces and aerodynamic surfaces, probably in approximately that order.
Thanks for your input Fred.
Some earlier comments mention that flutter could be the first symptom, some say that nothing would happen really except that acceleration would reach a maximum ...
I just don't know the answer to that question and I can see there is no consensus either on this Professional Pilots Forum.
What could be that maximum speed ?
... No clear cut answer !
All I can say is
Airbus does not tolerate any VMO exceeding, there must be a reason why ?
Also, and it is just a neutral observation, 9/11 was not possible the way the Story says it happened by using NG Airbuses ...