Even experts can't keep up with the changing rules. A spokesman for the European division of the industry's Airports Council International hadn't heard about Manchester Airport's new limit. A Southwest spokeswoman was grateful to learn about American's change; she was flying that airline the next day.
"It's the Wild West" on bag rules, the IATA spokesman said.
Here's how to avoid a showdown at the ticket counter:
Know before you go: Call the airline or consult its website. The IATA site offers handy links to nearly 100 airlines' policies; go to http://www.iata.org/ps/services/bags/links.htm .
Divide and conquer: Split your belongings between two bags. Just because you can wheel it to the ticket counter doesn't mean your bag will fly.
Devise a Plan B: What will you do if the airline makes you check your only piece of luggage, which you had planned to carry with you on a 17-hour journey?
That happened to my partner and me on a recent trip, when we ran afoul of a 15-pound carry-on limit on China Airlines. We frantically repacked in line at the LAX ticket counter, cramming inflatable pillows, eyeshades and more into our purses. I already had put needed medicines in my purse. What if I had forgotten them?
Take less stuff: There's no substitute for traveling light. For tips on how and what to pack, go to http://www.travelsense.org ; click on "Travel Tips" and "Packing" (American Society of Travel Agents) and http://www.ricksteves.com ; click on "Plan Your Trip" and "Travel Tips" (Rick Steves' Europe Through the Back Door tour company).
Hear more tips from Jane Engle on Travel Insider topics at latimes.com/engle. She welcomes comments but can't respond individually to letters and calls. Write to Travel Insider, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012, or e-mail firstname.lastname@example.org.