As far as I know you can generally get JFK right off the bat depending on your class seniority (by age). If not you should be able to get it in the following vacancy notice.

Reserve wait is kinda hard to say. There's been a lot of shifting around. All I can say is when I started in August the reserve wait for Detroit 900 (in terms of junior line holder DOH) was 4 years. Now according to the latest mock schedule for December the junior line holder is a June new hire.

I know that in MSP it's close to a millennium or two. That'll probably reduce to 25-30 years in a few months.