This question is for Airborne graduates. Are there any good workout routines that you used to increase fitness prior to school?

Run. A lot. Very slow.

CrossFit, Boot camp, TRX...and run. Alot. Make sure when you run, you find a place with cushion and where GOOD running shoes, otherwise you will give yourself stress fractures that will get worse when running in ABN school.

CPT (Join to see) All of the advice so far has been excellent advice. From what I have been able to learn about you, you already have a good exercise plan in place. Even though these items have been stated before, I will reiterate them.
1. Work on your pull-ups.
2. Insure that when doing an exercise, correct form is more important than number of repetitions - You can not get the number of repetitions without correct form.
3. Enjoy yourself.

I went right after Basic/AIT, the only thing you really need to be good at is running really slow.

I saw dozens (probably not enough) fail the APFT. Push-up form is very important. Be able to do pull-ups. I also saw at least one fail too many PT runs and get dropped. Be able to run for a few miles up and down small hills at a slow pace while sounding off with goofy cadences.

Stew Smith is my favorite source for military workouts.

Like CPT (Join to see) said, don't hurt yourself before you get there.

You mentioned in a comment that you were wondering about weight of gear; that's not an issue. There are no ruck marches. PT runs are normal PT runs in formation. The weight of the parachute is not something that you have to deal with very much.

All great comments prior to mine. IMHO as a former Co Cdr at the School, it's a blend of upper body strength (push ups/pull ups), slow long runs (7-8 min miles over 4-5 miles), and overall health/ fitness. I know I'm a couple of years removed but think about it, there are only 9 'formal' PT sessions with 9 record PT runs (after the initial PT test), averaging 8 minute miles at best, ranging from 2.4 to 5 miles (increasing every few days (2.4/3.2/4/5) through Ground and Tower Week). The Ground and Tower branch committees time each run (and each lap) to make sure that the company runs are within the standards. The majority of PT drops I saw (that were truly fitness related, not quitters) were either totally out of shape and never should have reported OR lacked overall fitness as the course takes a cumlative toll on your body over the weeks. You can X pull-ups/pull a slip NOW but can you do it after MANY push ups and pull ups wear down your arms. You can easily run an 8-minute mile over 5 miles NOW but can you do it after days of the Sling Land Trainer slamming you on your side practicing Parachute Landing Falls.

FYI I went though Abn School in '89 as an Infantry 2LT (D Co) and returned in '96-'97 as an Abn School Co Cdr (B Co). After PCSing from Benning I went to a ROTC assignment and mentored many cadets headed to Abn School. Don't overthink it. GOOD LUCK ! ! !

Pull-ups. I graduated in 1987 and it was a bit more physical than it is today. Just be in good shape and you will be fine

Mine was called Infantry Baaic/AIT right there on Fort Benning which had me in really good shape for Airborne School.

Run and pull ups

Running 4-5 mile clips, pull ups, pushups, situps, Airborne high jumpers, leg lifts/rolls. Sense of humor.