On the other hand, the US used an early cruise missle to deliver mail as a publicity stunt, and it did require landing[1]. IIRC the regulus system was develope

On the other hand, the US used an early cruise missle to deliver mail as a publicity stunt, and it did require landing[1]. IIRC the regulus system was developed as a reusable airframe to keep development costs low. [1]https://postalmuseum.si.edu/collections/object-spotlight/regulus-mail.html https://postalmuseum.si.edu/collections/object-spotlight/reg...