Why your 22 inch bag doesn’t fit in a 22 inch sizer: Luggage sizes are usually listed by the dimensions of the packing area, excluding handles and wheels. Airline rules list dimensions inclusive of handles and wheels. So a 22-inch bag may be bigger than 22 inches, and may not fit in a 22-inch airline baggage sizer. (Tumi claims to have shortened its 22 inch bags to 22 inches in order to comply.)
United’s sizer is actually 23 inches… and that’s why Travelpro 22 inch bags don’t fit in American or Delta sizers. United goes in waves but has been known to enforce carry on sizes at the gate. Their baggage sizer is actually more generous than their published rules — instead of 22 x 9 x 14, the sizers are 23 x 10 x 15. TravelPro tests its bags to fit in United bag sizers… but fitting in a United sizer does not mean it will fit in Delta’s or American’s which are actually built to published specs.
At least US airlines don’t weigh carry ons. Many non-US airlines weigh carry ons, and the weight limits are (to a US perspective) absurdly low. Sometimes you can avoid the weight check simply by checkin in online or at a kiosk. The goal is to avoid scrutiny. I’ve been made to check my legal size carry on by Air France for being over weight and fortunately planned ahead with a small carry on for my Virgin Australia weigh in earlier this year. Some airlines tag carry ons and check the tags which certify either or both acceptable size and weight.
Alaska has the most generous carry on policy in the industry. A representative from Alaska Airlines Mileage Plan once tried to get some advance info out of me on results from the Freddie Awards, with the creative inquiry — he just wanted to know what kind of luggage to bring with him to the event. I replied that he didn’t need to worry about carry on size since Alaska has the most generous carry on policy in the industry allowing 24 inch bags (24 x 17 x 10) explicitly including wheels and handles. Alaska is also putting larger capacity overhead bins into their 737-900ERs which will hold up to 48% more carry on bags.
Free vs. paid carry ons. Fly Spirit Airlines and there are two carry on size rules — how big a bag you can bring onboard for free, and how much larger that bag can be for a fee (when you’ll require overhead space). And you’d better know the difference before getting to the gate where carry on fees become prohibitive (the standard fee is $35 but at the gate $100).
How big can your personal item be? Some airlines like American just say it has to be smaller than your carry on. British Airways publishes allowable dimensions, and shrunk those this year 43% to 16 x 12 x 6.