Delta, Emirates and Lufthansa.

I prefer Jet Blue all the way. AA, DL & UA just not on my list.

United, Emirates and Lufthansa. Although I think I only prefer United because they maintain a large in DEN and so I don't get much of a chance to fly on other airlines.

None of them are actually on my list, although sometimes their daughter airlines might be. For example in case of Air France / KLM, I'd never fly either of them but I might fly Transavia which is ultimately owned by Air France / KLM.

United just because of the mileage, EK network and consistency, LH or KL, but not AF.

I am still a big American fan, but Delta has been catching my eye recently in terms of improvements to passenger experience, while United (aside from Polaris) increasingly feels like an LCC back in cattle class on their 737s. Nonetheless my list is:
1. American
2. Emirates (purely because they started FLL)
3. IAG

I used to be pretty loyal to AA, the main reason was because I had to fly MIA-DCA about once a month, and second they used to have a great FF program. But those days are long gone. They used to be more about being a "mainline" carrier and rewarding loyalty. They are just like all the others now, with bogus economy saver, less room in their new planes, getting rid of seat back tvs. Like most things in the world, service and quality continues to go down, but prices up.

I still like their product for international flying on long haul, the 77W 787 and retrofit 772 have a pretty good economy product (I preferred 2-5-2 of course) and their J product is good for when I do get to fly it.

But for domestic flying, and for my favorite U.S. airline it would have to be JetBlue. Even they are cutting down on the legroom, but it will still be better than the rest.

Never flown any of the ME carriers, so I would just go with EK because I want to fly them.

I would go with British on the Euro carriers, have flown them before, and will be flying them again. Their product is decent, at least compared to U.S. airlines. And they will continue to fly the 747-400 until 2024, that is the main reason I like them. Though LH has the 748 and 744 too.

1. United - I live in Houston so why not? I don't see any major differences between the big 3. If IAH wasn't a hub for one, but a large focus city for all 3. I'd go with price, schedule, and aircraft type without loyalty to any particular carrier. Of course, if I had a credit card that only earned miles on one particular carrier that would also drive my decision. American, United, and Delta are all the same to me.

2. Qatar. And I want a suite! (But seriously, I'd be very excited to fly any one of those three)
3. KLM

As for question #1, either United or Delta, but not AA as I had such a bad experience on an AA flight that I'll never - not ever - go back again.

You also didn't mention the next tier U.S. operators, like HA, AS, F9 or NK. We have used AS from time to time, too and have had generally good results. The only negatives about AS have been the pilot staffing issues at Horizon.

Wouldn't this thread be better suited in the Travel Pools & Preferences forum!

Delta, Qatar, Lufthansa Group.

1. DL
2. EY
3. AF/KL (mostly KL).

Wait, all of them have some form partnership with Jet Airways!

1. Delta (They keep adding where UA & AA are subtracting from passenger experience, Also J experience more consistent on DL)
2. Qatar (J Suites are Legit, Emirates J with MIDDLE SEAT in 2017 )
3. AF/KL ( I wish KL went all Aisle Access in J like their 787, and AF BEST)

IAG in J: BA is pathetic, Iberia and others Meh
Lufthansa Group in J: Passable...except LH until they update there 2-2-2 footsies

1) American.
2) Never flows on any, EK seems to have the route network and consistency, but Qatar seems to have the best product, so probably QR
3) only ever flown IAG, but I’d definitely be willing to try out others. I’ll tentatively say LH for now.

1.) Delta. Though I've never flown on them and none of the three are perfect, from what I know I personally feel like they're not as bad in terms of PR and customer service. I haven't flown very much on the other two to have a firm opinion; I have no problem with them.

2.) Ehh

3.) Lufthansa, the only European carrier I've flown with listed (and only one aside from Niki Air). I did have a pleasant time on their planes I guess...