I just returned from Holland with my 6.6kg (15lb) Boston Terrier. I traveled on a "companion pass" from my UA employee friend. the dog flew at my feet on all flight legs. The airline did charge me US$125 for the return on United. The outbound flight was at no charge but I will chalk this up to the "unwritten benefit code" awarded to employees and their friends.
Entry into EU at AMS was easy. Customs didn't even ask for the EU Veterinary Certificate I had had my vet prepare.
On the return, the check in staff at AMS are not UAL employees so everything is by the book. They even wanted to see the dog's health documents req'd for entry into EU, even though we were leaving the country! They were the most bureaucratic (but friendly) people I have ever seen in W. Europe. The dog seemed to throw them for a loop.
At no time was the dog ever weighed. It would probably be easy to have taken a dog up to 8kg (18lbs) in the cabin with you. No one ever examined the carrier either which has a broken zipper that doesn't close. My dog is well behaved and never makes a sound. I even had him snooze under the blanket on my lap for a few hours.
Overall, experience was good. Holland is not the most dog friendly country.
Muslim restauranteurs do not like your dog with you even at sidewalk tables.
In Amsterdam, I used
www.Doggiedog.nl for a couple of day care days while I went to museums. They were cheaper than U.S. dog care! Recommended.
Entry back into the U.S. is always easy. Customs has never asked me for any documents for the dog on any of my four entries into U.S. However, they can make a big deal about having
dog food which depending upon the agent, is a big no-no. In 2006, I had a bag of Canadian Pedigree confiscated at the N.Dakota border. If you need some dog food carry two servings in a plastic bag. That seems to satisfy them.
Good luck with your canine friends!
Chris
San Francisco, USA