The number of fluid ounces you can take on a plane in your carry-on luggage is generally limited by the TSA 3-1-1 rule, which allows liquids in containers of 3.4 ounces (100 milliliters) or less. All containers must fit inside one clear, resealable quart-size bag, roughly amounting to about 25-26 fluid ounces total in carry-on.

However, there are some recent developments and variations by airport:

• In the US, the 3.4 oz (100 ml) limit per container and the quart-size bag rule is still enforced nationwide with no official timeline for change.

• In the UK, some airports like Edinburgh and Birmingham have adopted a new allowance of liquids up to 2 liters per container in carry-on baggage, without the need to remove them at security. Other UK airports still apply the 100 ml rule.

• Certain liquids like prescription medication, baby formula, and medically necessary liquids are exempt from the 3.4 oz limit but may require additional screening.

Summary:

• US flights: Maximum 3.4 oz per container, all must fit in a single quart-sized bag, total around 25 oz.
• Some UK airports now allow up to 2 liters per container in carry-on.
• Checked luggage generally has fewer restrictions on liquid quantities, but some liquids are prohibited entirely.

This means for a typical US or many international flights, you can take multiple containers of up to 3.4 fluid ounces each, as long as they all fit in one quart-sized bag, which practically limits the total amount of carry-on liquids to about 25-26 fluid ounces. Exceptions and changes might apply depending on the airport and country of departure.