Which national flag carrier has the best inflight meal or drink snack menu

None !!!!! All are tolerable but just.

Which seating class?

Lets be clear on what the 'subject' is

So the one person who has flown all the national flag carriers in all classes, and is thus in a position to judge, is on a gluten-free diet.

I’m with Frank on this one.

I primarily fly Delta and airlines that are associated with it like Air France, KLM and Korean Airlines.

I haven't flown Alaska Airlines, but have flown American Airlines and United. Delta seems to be better than those two.

For international airlines, Air France is excellent as well as Korean Airlines. KLM is good, but not as good as the other two.

Haven't flown Luftahansa in a while, but I know they are good.

Also, recently did flights on Egypt Air and Qatar Airways. The food was not bad on either, but for other reasons, I don't plan to fly on either of those airlines in the future.

I also agree they're all mediocre. I've flow first class (twice), coach a hundred times, and premium economy only recently because coach sucks. I've never had a meal that exceeded being just OK. It's free and something to occupy time on a flight, so I eat it most of the time. On occasion it looks, tastes, or smells funny and I just eat my snacks.

Japan Airlines (economy class)

Turkish Air, even in Economy class

Last year we did Austrian Air First Class from Venice to Vienna to Chicago. The food was exceptional.

Best Bread? Probably none of them because I don't recall thinking this is the best bread I have ever had when eating airline food in any class. Airline food maybe 30 years ago was much better, especially breakfast. Today airline food is so bland because almost everyone is allergic to something. Business class to Europe on American has very good snacks.

Find a carrier based out of an Asian country you’re going to do much better than any based out of Europe or America. I’ve done Singapore airlines, and while I haven’t done every national carrier, they far exceeded any other airline I’ve ever been on which includes Delta, American, United, Virgin Atlantic,Air France, British Air

The consensus among most frequent flyer sites that rate airlines seems to be Asian airlines just do a better job

https://www.youtube.com/watch?v=qt2-0D-IDP4

Jeb and Suzanne Brooks and my mate Dennis and Julie Bunnik have high praise for Singapore. Cannot disagree.
Maybe compensates for extra distances to Europe. 7 Mile high club in comfort?

I echo Frank on the first question. As to bread, it always puzzles me that despite originating in San Francisco, a city known for fantastic bread options, we’ve always been served tasteless, slightly stale rolls on flights from there.
We did get decent food on Korean and on Turkish. Imo, the booby prize goes to United/Lufthansa. We haven’t flown internationally since the pandemic, but I somehow doubt things have improved.
Years ago, the advice was to obtain a better meal by ordering kosher. I suspect that nowadays that would result in a vegan, salt-free, gluten-free, dairy-free (taste-free) offering. In the last few years, our ploy has been to get our own food to bring on.

I've eaten some very good food in first class on British Airways and considering the limitations posed I was quite impressed. Virgin's Upper Class also served some great food. Breakfast on both airlines in those classes was poor however that is usually down to the catering providers at the departure country.

Both provided excellent wine choices, BA better than Virgin however both have reduced their selection over the years.

The food rapidly deteriorates in quality and standard as you descend class.

By reputation, Emirates top class (and most expensive) can be good dining. I'd like to find out.

"National" or "flag" carrier is an out-of-date distinction.

None !!!!! All are tolerable but just.

I am with Frank, although "tolerable" may be exaggerating a bit. (To be fair, I have never flown any of the Asian airlines.)

And bread on a plane ? None of it is any good (says she who lives three blocks from Paris's 2023 Best Baguette) 🥖🇫🇷🏆

There are a number of surveys published online and none are very consistent. The names that pop up the most for being good in Economy Class are Turkish Air and Air France. My experiene has been that Turkish Air is not terrible at all. SkyTrax also rated them them towards the top overall, and at the top if you just look at European airlines.

Some years ago saw a TV program on the "behind the scenes" of how stuff happens/works.

One segment, on airline catering, was interesting in it's exploration of the challenges in making a meal for airline passengers.
Some of the factors are the obvious , budget, refrigeration, (re) heating, packaging for transport.
What was news to me was that it revealed that human taste bud, and to some extent smell, work differently in the drier air in an airplane and being pressurized differently than natural ground level has some adverse affect. Also the food dries out more quickly in the cabin air.

Finding ways to prepare and season foods so they come out 'right' in an airplane in flight is more of a challenge than fixing a good meal on the ground.

Having flown international biz on Delta, BA and AA, I could not rate one clearly superior to the others

My mate Sam posted this on his YouTube channel recently.

Hope you find it interesting.

https://www.youtube.com/watch?v=T76yE8RH6jg&t=130s

Emirates is my long-haul choice.