Fanny packs. Cross-body bags. Shopping bags. Pillows and blankets. 

The Southwest Airlines  gate agent rattled off so many items that counted toward the two carry-on bag limit on my flight to Baltimore, I thought it might be a playful jab at Spirit  and Frontier and their rigid carry-on policing to collect more fees.

But this was no joke. Southwest quietly began cracking down on carry-on bags on Feb. 22, ahead of the spring and summer travel rush, advising gate agents of the changes in a memo. This crackdown isn't about bag size. It is about how many bags you have.