Just try to imagine this as mass transit:

Meet the Martin Jetpack, a contraption unveiled at a US air show yesterday. It is a real-life version of the toy we all fantasised about as children (and some of us as adults) and which Sean Connery as James Bond got to wear in the early minutes of Thunderball. Simply attach, the manufacturers claim, and up you go. No more traffic jams as you slice through the air at speeds of up to 186mph.

OK, try to imagine 186mph.  In the air.  With a thousand other idiots flying through the air around you.

I've done about 120mph on a Kawasaki and that was an interesting enough experience in two-dimensional transportation.

I can't even begin to imagine adding another at that speed.