How strict is Delta/Air France with carry on size?

Patrice- My wife and I purchased the RS convertible carry on bag and traveled on Air France with no problems at all.

No problems with Delta. But I have had to drop my bag in the measurement box on Air France flights booked through Delta. Since I never pack it completely full, the bag fits easily. Still it is annoying that they always want to test my bag while my wife's overstuffed roll-on bag is never challenged.

I've had no problem with DL or AF questioning my RS Classic carry-on, but did have to use the sizing frame on a Czech Airlines flight. My bag was stuffed but compressible with no rigid wheelie frame and easily stuffed into the sizer.

The question of how strict in the past may be less relevant than a future tense question of how strict will airlines be in the future. With the high cost of checked bags domestically and of extra bags internationally, in cabin baggage space is getting dear. That and the trend to hard framed rollers cutting into cabin baggage capacity is a trending problem. Hence the American Air et al more restrictive carry-on size. A marginal carryon bag today may be a must check bag tomorrow.

I've had them allow me to carry it on from the US, but make me gate check it when changing planes in Europe (albeit, to a slightly smaller plane). With that type of gate check, I take almost everything out of my checked bag and put it in a light weight tote. That way I've got my stuff with me when I arrive at my destination. And if they lose my luggage, they're only losing a mostly empty suitcase.