If the script isn’t in your game then there shouldn’t be an error. Did you possibly drag that script into a random Part and it’s still there?
You should be able to follow the link to where the item is that is erroring, so if ‘user_Falcon Airlines A320.rbxmx…PlaneKit.Regeneration’ doesn’t have a ‘Regen’ in it that’s why you’re getting the error.
You could use the search at the top of the Explorer window and use the term ‘script’. That will show you all the scripts in your game. If you find an extra script that’s causing the error then delete it.
Looks like it might be a plugin? I see .rbxmx on the output have you tried deleting all your plugins or finding it in the plugins folder? Load up an empty baseplate and load everything you have in the plugins folder maybe you’ll find it.