To be honest even current airtravel is mostly done single pilot in reality. Up to 14 hours flight duty with just two pilots means that usually one of both is napping and the other one is trying very hard indeed to stay awake, doesn't always work out as the transavia incident a few months back showed. Doing the same with three pilots on duties up to 18 hours rostered (and 21 hours with disgression) just means the same, with the added bonus that one of them can rotate out to sleep in a bunk inbetween.