I can't seem to find out what year pepsi (or coke) started shipping plastic bottles only. Was it all at once or did they switch gradually?

Wow, I'm not real sure.  But, it seems like the plastic bottles (then 16 oz., now 20 oz.) started in the mid-80s.  I remember Pepsi and Coke being in glass bottles a few years after that because my dad is an avid Pepsi drinker and I used to have to go to the store to get them for him.  I would guess late 80s or early 90s were the demise of the glass bottles.  Of course, this is by no means factual, just what comes up from my memory.   :)

Coke and Pepsi come in plastic bottles?
I guess the Island I live on is a bit behind the times, still all glass all the time here.

I still wish Coca-Cola came in glass bottles, I thought it tasted better and a lot more environmentally friendly.  I know that Coke was available in 600 ml glass bottles in 1992 that looked like the old beer "stubbies".  I believe they switched over to the plastic replicas of the old glass bottles (pre-1970's) in 1993.  Mind you it really depends on what country you are in.

I think the 2 litre bottles went plastic in 1979 or 1980.  I can remember the size being "new" and shortly there after the bottles started exploding and maiming (killing  ???) people.  I think they went plastic real quick for obvious reasons!

I remember "pre 2-liter" bottles were 32 oz. here in the US and they were glass.  I forgot all about those.   :)