There was a 3 part program on the Discovery Channel a few months ago about a very large model rocket meet in Kansas. These guys launched thousands of model rockets (one group from Colorado Springs set a world record by launching over 200 at once). There were rockets there that were powered by hybrid engines and one monster that had a homemade solid rocket motor that used the same mixture as the Shuttle SRBs. That was the one that exceeded Mach 2 and 40,000 feet as verified by GPS and telemetry. Clearly, there are people out there who're building things that are far larger and more powerful than anything sold by Estes. Now, whether anyone capable of building such a rocket would launch it offshore and especially anywhere near an airliner is another matter.