Originally Posted by
cyru5
These are all old maps, from when T1 was Concourse C, and T3 was Concourse A & B. You can freely walk between A, B & C Concourses. So, until about 2015 you could walk between T1 & T3 airside (but not the check in areas).
Now T1 only handles Concourse D, which is a separate terminal.