This is something I don't quite get. Why is spell casting necessary to travel to diverse locations, including other planes? Or to put it another way, how is a group of D&D players meant to work out that an ability/skill check - probably Intelligence (Arcana) - can't be used to find a way between planes?
Page 5 of the Basic PDF talks about the fundamental importance of magic, and links it to chapters 10 and 11 (ie not the chapters about ability checks). But how do we know that it needs magic, in that sense, to travel between planes? Why can't a fighter use a skill check to find a magical crossing or portal?