Latest requirements for carry on bags

It varies by airline. I'd have to go to individual airline websites to find out; you can do that.

In the past it's been 22"x14"x9" for US carriers and 55cm x 40cm x 20 cm (21.65"x15.75"x7.87") for European airlines, but some European carriers have now gone to 55cm x 40cm x 23cm (21.65"x15.75"x9").

A lot of US airlines don't have weight limits on carryon bags. Some European airlines (Lufthansa) restrict them to 8kg (17.6#), others 10kg (22#), others 12kg (25.4#).

"In the past it's been 22"x14"x9" for US carriers and 55cm x 40cm x 20 cm (22.65"x15.75"x7.87") for European airlines, but some of them have now gone to 55cm x 40cm x 23cm (22.65"x15.75"x9")."

Transposition error?

I believe that a number of US carriers recently reduced the width down to 14" or 35cm not increased max width.

The with seat pitch down to 32" or 31" bags need to be narrowed accordingly. A single aisle aircraft with a 31" seat pitch can only accommodate 2 carry-on bags each side. In a 3+3 economy configuration that means only 2 of 3 passengers can store 14" wide baggage on a fully loaded flight.

http://www.aa.com/i18n/travel-information/baggage/carryon-allowance.jsp?locale=en_HK

The maximum dimensions for your carry-on are the following
measurements: 56cm(l) x 36cm(w) x 23cm(h) or 22in(l) x 14in(w) x
9in(h). All carry-on items should be stowed in an overhead bin.

http://www.delta.com/content/www/en_US/traveling-with-us/baggage/during-your-trip/carry-on.html

Baggage must fit easily in the Carry-on Baggage Check (approximately
22" x 14" x 9" or 56 x 35 x 23 cm), which is located near the
check-in counters

http://www.united.com/web/en-US/content/travel/baggage/carryon.aspx

Carry-on bag: The maximum dimensions for a carry-on bag are 9 inches x
14 inches x 22 inches (22 cm x 35 cm x 56 cm), including handles and
wheels.

You should check limitations of regionals, be the domestic or foreign, in that the puddle jumpers have tignter compartments.

Air France is:

21X13X9 - 26lb

Lufthansa says their size limit is 55cm x 40cm x 23cm (21.65"x15.75"x9").

Sorry, I wrote 22.65" for 55cm converted to inches; it's 21.65", slightly less than the US limit.

As long as I have been following carryon baggage limits, it always been 22"x14"x9" for US carriers (I just found an Excel file from 2008 in which I was comparing United and Lufthansa size limits and United was 22x14x9 back then, almost 9 years ago).

"Air France says, To be accepted in the cabin, your hand baggage must not exceed the following dimensions: 55 x 35 x 25 cm / 21 x 13 x 9 in (including pockets, wheels and handles)". 55x35x15 is 21.65 x 13.78 x 9.8, not 21 x 13 x 9. I guess they are rounding down to whole numbers, but I doubt that the measure it in inches.

Whichever airline you finally book on, ask about the baggage restrictions. Surely that is the simplest answer.

Eddie, I know this is heresy, but -- you CAN check a bag. Sometimes it's just easier to pay the additional $25 on an intra-European flight rather than worrying about it. On our recent trans-Atlantic flights one checked bag came free.
And come join us at the San Francisco area (Larkspur Landing) meeting on the second Saturday or Sacramento meeting on third Saturday.

I agree with Laura.

Most of the flights from the US to Europe include one free checked bag. And, if you are making a connection but are all on one ticket, that baggage allowance applies to the flight within Europe as well. For instance, if you're flying Boston to Paris to Warsaw all on one ticket, you get one free checked bag (within the size and weight limits) included for the whole way.

But yes, as to your original question, the restrictions for carry on bags used to be more uniform, but now vary from airline to airline. And the same airline will have different rules for trans-Atlantic flights and other flights (I got caught with this on Turkish Air - their trans-Atlantic carry on allowance was generous, their allowance within Turkey was much stricter).