[rippercushions]

LOIs are nearly free. They're basically securing a spot at the front of the line just in case Boom manages to deliver.

Unlike Theranos, supersonic engines already exist and they are regularly used by the military. The issue is that none of the big boys are willing to pony up a lot of money to build, test and certify one for civilian use unless they can definitely get paid for their effort.

And yes, there are willing buyers who will pay ludicrous amounts for comfort or speed, as the increasingly elaborate arms race in first class (eg. multi-room suites a la Etihad's Residence) and the entire private jet market demonstrate. The Concorde was profitable towards the end of its life despite mind-bogglingly high fuel costs, so there's definitely a market if -- and it's a big if -- Boom can pull it off.