I have a few bottles of toiletries with flip-top caps. Are those more likely to leak (w/airplane pressure and all) than regular, non-flipping caps? (This is a serious question. And yes, I'm putting them all in ziplock bags just in case anyway.)

The only time I've ever had a bottle leak (and I use all sorts of caps, including flip top) was when I filled it too full. It didn't leake through the opening in the top, rather from the neck.

Best is no more that 2/3-3/4 full.

A regular screwtop can only be open when unscrewed, a flip-top can be flipped opened with much more ease.

If they're in plastic bags there's no real problem. You are worrying over such an irrelevant issue - make your own mind up!

Yes, they can leak. This happened to me once, and I now put anything likely to leak in a zip-lock plastic bag.

I've had 2 caps leak over the years, and both were screw on kinds. The very top is often seamed and cracks if twisted too tight. Good point about the flip top but I've never had a problem.

Yes, flip-tops can leak. I was planning to take Roger & Gallet shower gel on holiday but decided against it once I saw how the gel oozed out when the container was standing upright on my bath. I'll go with screw-top from now on, when travel is involved.

It's not an irrelevant issue, in my view.

Physics lesson: the cabin of an airplane (including the luggage hold) is typically pressurized to about 9,000 feet. Since your bottles contain air at sea level pressure (several pounds per square inch higher than cabin altitude), the tendency is for the pressure to force the caps open and push out the contents. The same is true of the air inside the ZipLoc bags.

Buy some screw-top travel bottles for your liquids. Or buy your toiletries when you arrive.

I put elastic bands on flip cap bottles (the elastic goes vertically around the botton and cap and then i put them in a plastic bag.

Have been using flip top toiletries for years with no problems. If the flip top is secure - and if the bottle is no more than about 3/4 full you should be fine. But, test the caps before you go. (Also, for safety I put all the toiletries in a plastic-lined toiletry bag - Liberty has really pretty ones with all little empty bottles and bands/pouches to hold everything in place.)

As noted above, if the caps are loose or cracked at all - or if any of the bottles is full or even near full - the difference in air pressure will cause leakage.

I work in the cosmetics field and I can tell you even screw top bottles may leak. My own mother complains that her liquid make-up always seems to ooze from the bottle. Does not seem to matter if it is in the carryon or the checked bag.

So just to be sure bag everything and make sure that the stuff around it is not going to be a problem if there is a leak.

Good Luck.

We typically use flip top bottles made of the somewhat flexible plastic. I usually fill them about 3/4 full or so then squeeze them slightly and close the top. I've never had one leak. Fluids generally do not compress or expand but any air in the container (or absorbed in the fluid)will. But I still put them in zip-lock bags with most of the air squeezed out.

Thank you all for your help. I did indeed take the flip-top bottles with no leaking problems. Took all your suggestions - filled only up to 3/4 full, squeezed out excess air, then put them in ziplock bags. Worked like a charm through multiple flights. Thanks again.