After the defeat of the Tsukasa empire everyone was relaxing all but Senku who when having nothing to do on this day sat thinking up plans for the future.
Chrome having gone exploring hears a strange noise from the sky when he looks up to see what it is he gets scared and runs back to inform the others about the strange thing flying towards the hot springs.
When Chrome got back to where everyone else was he told them what he saw and then everyone went to investigate, when they got to where Chrome saw this flying thing Senku was so surprised that he started running to where it landed.
'What's a plane doing here was there someone else who revived before us but never came here till now?!' Senku thinks while he's running
"Hey Senku do you know what that is?" Chrome asks
"Yes, I do know, that is an airplane it was a form of travel in the past that let's you soar through the sky like a bird" Senku tells him "The only problem is how is one here now? That's what I want to know."
When they reached the plane the ramp was down and there were people getting off. When Senku saw who was on board he knew that they would be a huge help with finding out what caused the petrification of every human on earth.