I'd just dive right in and do it. Life rarely arranges itself neatly in fifteen week intervals, in my experience
Seriously, though, travelling doesn't have to be a barrier. I travel nearly constantly, seems like - most months at least one week, many months two or three weeks, with two or three days home in a row. It was no exception when I started Meso 1. I often did the workouts three in a row, or three days out of four. I'd arrange the set with Legs as the middle day, and whenever possible I'd also add a 'cardio only' day between the Triceps/Legs so as to rest my back.
Even at that, Meso 1 still gave me terrific results in strength (that's my goal for the series). I am on the six month plan, yet increasing the weight of essentially everything each week, so as to be tired enough at the end of each set
And I'm lifting so much heavier than I ever thought possible. 100 pounds on a deadlift???? Not wonderful by what some people do here, but I recall being so proud when I had to move up to a pair of fifteen pound dumbbells for that.
Meso 2 is proving to be more than a challenge. I've been travelling most of the past three weeks and doing the heavier workouts back to back on sleep deficit is taking more of a toll. My new plan is to add gaps by thinking of the 'workout week' as a suite of ten days, and stretch each trio of exercises out over this longer period. If I choose to spread a "suite" of STS over ten days rather than seven, that should help my body through a little longer between each session for repair and recovery. I'll let you know how that goes, if you're interested. I am just finishing week 2 (second time through) on the usual three a week method, and with this three-in-ten-days approach it should take me about 40 days to get the next two weeks done. Fortunately that's when the travel situation will lighten up, just in time for Meso 3.
The trick to doing strength training after a crosscountry trip is to get enough sleep *and water in your muscles* so that you are not exhausted when you start. A catnap before starting can help, and being really disciplined in drinking your water on the plane trip home makes a huge difference.