Hi Kathy, sorry, I've only just seen your question....... (I can blame Frank, I'm busy in minimalist mode in my house).
The ECAW is a bit smaller than a couple of bags I've used in the past and they fit under every seat of the different planes I've flown on.
To qualify that statement, my international flights between Canada - UK are either British Airways or Air Canada (777-300 / 763-300 & Embraer 170 / 190), I haven't flown anything smaller where, I should imagine, under-seat space would also be minimal.
The secret is to not over stuff your bag, keep the depth at 8 inches (the depth size of the bag) or even allowing it to expand another inch, as most under-seat space allows 9 inches.
I practice pack about 4 weeks before a trip, start getting really serious with my packing list, check weather forecasts of my destinations to get an idea, also mentally do my trip and think about what I'd wear for travelling about on transport or different situations i.e. evenings out, slouching around indoors, any special occasions to attend. Then about a week before, I start talking to myself whilst standing in my closet matching colours, choosing clothes........something I do when my husband is at work otherwise he'd have me sectioned off! LOL!
My experience is, the less clothes (and colours) I have to choose from on the trip, the more time I have going out and doing what I went there for. Next time I will be black, navy, denim and white, with a couple of colours to pop.
Don't know if anyone has given you these sites but they're helpful for ideas.........
If you go into the blog files, she has done every colour imaginable.
Love this site, I've down loaded all her lists and PDFs.
Good luck and make the packing part of the trip fun.......otherwise it could send you crazy. 😉