Liquids in carry on, why and how much?

A "quart" is a unit of measurement - about 0.945 litres. It's a standard bag size in the US, if you google for "quart resealable bag" and click on "Images" you can get an idea of the size. In my experience, the TSA is not strict about the "resealable bag" part, especially if you don't have many liquids, and if you just show them 2 small (<100ml) items they will easily let you through.

To answer your question:

I fail to see why I would need a resealable plastic bag. Resealable bags are not common here and I prefer to just keep them organised in my carry on, instead of in a plastic bag.

There are a number of practicalities of using a resealable plastic bag for both the security officer and yourself:

1. Everything is on show in one place inside the bag without opening it.
2. The seal stops any liquids or containers escaping.
3. The bag can be opened and closed quickly by either party.
4. The 1 litre size stops the passenger from bringing more than allowed (to some extent)
5. The uniformed size and style makes the process of checking liquids in hand luggage the same for all. In theory all airports adopt the same process (in reality there are many subtle differences that different airports use just to keep you on your toes)

In my TSA experience, I've never had any problem with bigger bags, just as long as the liquid containers itself are <100 ml. Also, at every TSA checkpoint i've been (IAD,EWR,JFK,LAX), while waiting in line, there's free bags you can grab to put your liquids in. So just keep them in your carry-on, put them in the free TSA bags while going through the checkpoint and when you're through put them back in your carryon.

To address the why part of the question, all these rules date back to the summer of 2006, when it was announced that UK security services had learnt of and foiled a plot to attack a flight from London to the US using a liquid binary explosive. That is to say a bomb made by mixing a couple of safer parts together to make a more dangerous one.

The immediate response was mostly to ban people taking any liquid whatsoever onto flights with them. This wasn't popular, especially with the duty free shops, and the rules were eventually relaxed towards the type we have today, where liquids brought through security from landside have to meet maximum volume limits, both individually (the 100ml/4 ounce limit) and in bulk (fitting into the prescribed size of bag). Sources are divided on whether this makes us significantly safer, but those are the rules, and depending on the airport and level of alertness, not obeying them might lead to complications catching your flight.

In most flights that I've been on, there are all kinds of bags of varying size and shape. I personally use a little clear zipper bag that you get when you buy a set of small airline approved toiletries or containers.

Since you have these items organized in your carry-on, you probably have them in a bag already. If it was a clear bag, you're all set. If not, I'd still give it a try, just remember to take it out of your carry-on. Worst case is you have to go get a little baggie by the wall over there (!) and put your stuff in it. I've never seen anyone complain about the size or shape of the bag, but always the full size bottles of sunscreen, shampoo, lotion or toothpaste that people still insist on bringing. Don't be that person. Get smaller travel sized items or buy it when you get there.

There have even been times when I forgot to take the bag out of my carry-on and didn't get stopped. And I'm a person that refuses the cancer scanner!

Basically, if you make it convenient for them to see what kind of liquids/gels/etc (usually toiletries) you're bringing with you without them having to open your bag the less hassle you'll get. If you have all the correct sizes of things, they should all pretty much fit, and again, the less hassle you'll get. Not even a second look, I guarantee.

Having to open your carry-on will just cause a delay for everyone else down the line and that's why you will want to take it out. Having items like that in your bag might also invite you to a pat down, cuz that's how we roll here now.

Happy Flying :)

The TSA rules only apply when entering terminals in the United States, but that does include domestic connections from international arrivals.

The resealable bag is a Ziptop/Ziplock style bag. Ziploc Storage Bags - 1 qt. See this diagram by the TSA.

But I have also witnessed people with much larger bags, but clearly compliant liquid amounts.

The reason they ask for this is so the bags of 100ml liquids containers can be put through the x-ray separately, outside any luggage.

Despite the lax enforcement I've witnessed lately, you should still comply just in case.