The KLM site has a good description of it. Within Europe they go by weight only, regardless of the number of pieces. For international and code share flights they go by piece, but still with (higher) weight limits

And we do have it good. For comparison, I just looked up two 300 mile trips on non RJ jets, cheap economy ticket, flyer with no elite status, no oddball oversize or overweight bags.

NW on a DC 9: Carry on one 45 inch dimension bag, plus one accessory (briefcase, laptop, or backpack), no weight limit. Checked: one bag, max 50 pounds. To check a second 50 pound bag is $25. So NW will carry 100 pounds checked for $25 total surcharge one way.

KLM on a 737: Suppose on an AMS vacation you want to make a side trip to Berlin and buy a local tic not related to TATL travel. Carry on one 45 inch bag plus accessories, max weight total for bag and accessories 12 kg/26.4 pounds. Checked baggage weight 20 kg/44 pounds.

Close so far, but if you are a typical too much baggage Americal tourist, watch out. For your checked bag, anything over your 44 pound allowance is 12 Euro per KG One Way. That is USD $8.17 per pound one way. To check the same 100 pounds is a $457.52 surcharge.

Got baggage in AMS? Take the train to Berlin.

Agreed.

(copied from another forum)
It would be perfectly fair to put up a pay station in the gate area. You would pay for checkable bags whether or not you succeeded in carrying them into the cabin. You would not pay for qualifying carry-on bags whether or not some got gate checked. If you skipped the pay station and headed for the jetway, you might get singled out and sent back to pay for items. If time got short, the pay station might close up without processing everybody who then proceeds to the jetway.

Actually they should have started charging for carry-ons before this first checked bag issue came up. Speed up boarding and/or enjoy a big cash cow.

Travel tips: http://members.aol.com/ajaynejr/travel.htm

OK, it childish of me. But if AA is trying to increase revenue by charging $15 for the 1st checked bag, I say that you make sure that your checked bag is as heavy as permitted before going to the airport by packing a rock or two in your bag. This way, the combined effect over many travelers would be increased fuel consumption and defeat the revenue generating angle. If you over-estimate your weight, just pull out your rock and have agent re-weigh your bag.

its a good idea, but you realize it would do nothing other than to increase the charge for the first bag or remove elite allowances, unless the airline were aware of what you were doing.