I haven't yet travelled with my B35, although I would love to. Bringing it to Singapore is a no-go unfortunately, due to nosy and intrusive relatives, which is a damn shame, because I think it would have worked well there.
Also, on the basis that I only ever travel economy, I am so nervous about having to squish it under the seat in front of me.
I am planning to make a trip to Dubai soon, and I am definitely keen on taking the Birkin with me then. I think the plan would be to store it on its back in the dustbag at the bottom of my cabin bag, surrounded by soft clothing so that it doesn't get knocked about when I have to put the cabin bag in the overhead compartment, while using my Book Tote as my under-seat bag.
I did buy a great packable waterproof bag for the purpose of inclement weather, but I think it could be a great solution for those who want to carry their B35s in the cabin but wanted to protect it when going through security and storing the bag under the seat, if you're not too concerned about fitting it under the seat.
I can't praise them enough. They are big enough to fit B35s including the handles, and tiny once packed. I also use it to put the bag in if I'm travelling on crowded public transport.
Links for the US and UK below in case anyone is interested.
https://www.amazon.com/Mozzyyee-Portable-Foldable-Shopping-Multipurpose/dp/B0969CZD9Z
https://www.amazon.co.uk/Mozzyyee-Portable-Foldable-Multipurpose-Camouflage/dp/B0969CZD9Z/
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