LHR is capacity constrained right now so they don't have slots to add more flights. Hopefully the runway expansion will be finished by the time Boom airliners are actually in service.
Have to be charging a great deal to the small number of passengers for it to be worth swapping in to a fully loaded 777 spot
Edit: Apparently Overture is 65-88 seats depending on configuration.
You could also upgrade a couple of the 777-200 or 787 routes to a 777-300 to get more seat miles to offset those lost to loosing a slot to a smaller aircraft.
That's still two aircraft instead of one, which means acquiring another slot.
American already has several slots into LHR. I counted 24 arrivals into LHR tomorrow.
One 777 all economy plus one Boom aircraft all business is roughly equal in seat miles to 2x 777 (first + business + premium economy + economy).
An upstart airline would need to acquire a slot to get a new aircraft into LHR. However American could add a super sonic aircraft to its service and still maintain the number of the seats it has going in. Yes, it would have to take one aircraft out, but there are enough pax that will be connecting and can be sold a different routing that it can use flexibility with seat configuration to not be limited by slots.
For American, a bigger factor is probably what kind of seats they can sell. For instance, DFW->LHR has a 75% load factor tomorrow for first class but a 68% load factor for economy class. However, later in the week economy has a higher load factor.
Those first class seats are a lot more profitable than an economy. Adding first class seats while taking away economy seats is profitable if you can fill the first seats.
No, but it’s the only airport in London that the big US legacy carriers - American, Delta, and United - fly to.