Playing the game through for the umpteenth time and want to try something new but i don't want to waste my time. I have just beaten Spherimorph and got the First Jecht Sphere(also got the other one from Macalania Woods and Thunder Plains), but can i go all the way back through the game to Besaid from here to get the one from there or do I have to wait to get the Airship and therefore battle Dark Valeor to get it like all the other times?

You have to get on the Airship first
Thread over somone close it

Actually, someone said elsewhere in this forum that they went all the way back from there to get the Jecht Sphere in Besaid so that they didn't have to fight Dark Valefor. So, I'm pretty sure you can; unless that person was lying.

It's more easier to get the Jecht spheres if you have the airship, in my opinion.

It certainly speeds things up quite a bit.