personal item sizes for airlines, 2018 research, special notes for Delta and TAP Portugal

Frontier              18 x 14 x 8

Delta                   20 x 17 x 11 (smaller in window seat)

Air France/KLM  16 x 12 x 6

TAP Portugal      16 x 12 x 5 (max weight 4.4 lbs / 2kg)

T&L Article          20 x 17 x 11

CostCo sm bag  16 x 12 x 8   (may be thicker if stuffed full or expanded)

Fits Mult airlines 17 x 10 x 8 according to another T&L article

Conclusion: CostCo bag is legal personal item on many airlines, except Virgin and Air France/KLM/TAP Portugal,

and is only legal on United if you don't bring another carry-on

On Frontier, only the personal item is included in the fare.  On TAP Portugal and Delta a personal item and a carry-on are included.  Don't know about others.

For carry-on, a size of 22 x 14 x 8, max 17.5 lb, would be free on both Delta and TAP Portugal (total of 22 lbs in personal and carry-on bag on TAP)