We did Gina Ford with our DS and travelled with him at 5 months for the first time. I didn't change anything and the difference in daylight meant he just woke earlier (in our case) and I started the day then with his first feed.
How long are you going away for? If the routine is working well for you at 4mo I would just go with whatever happens while you're away, but still treat 7-7 as night time IYGWIM and then space your feeds as you normally do. Then when you come home it should be easier to get back to normal.
There are loads of threads around if you do a search about flying with a baby with some great advice. My "top tips" feed on the way up and on the descent if you can, otherwise if your baby takes a dummy use that (and get a dummy clip!!). If you have an umbrella stroller you can take it to the gate and it should be waiting for you at the other end when you get off the plane. A carrier (eg Moby or Ergo or sling etc) will give you two hands free and might be easier than a pram, I prefer to put C in the Ergo so I have hands free for bags.
Don't stress! It's easier than you think