Last week, United Airlines entered a conditional agreement to buy 15 planes from Boom Supersonic and become the first airline to offer commercial faster-than-sound travel since the Concorde stopped flying in 2003.

The deal is highly provisional. United is buying 15 of Boom’s Overture planes, but the Overture does not exist, per se, at the moment. Boom claims they will be able to deliver them around 2029, but United’s agreement to buy planes is conditional on that actually happening first and the aircraft passing safety tests and such. If it works out, and if the planes prove themselves to be commercially viable as well as technically feasible, United has the option of buying 35 more.

Of course, in the end, it might not amount to anything. But Boom is a pretty exciting company that’s been gaining momentum for years now and this is definitely another step forward for them. It’s exciting in part because fast planes are cool.

But reall…