Hey all, not sure how an airline discussion ended up on an Amtrak forum, but if you'll indulge me it's the only thing I'm knowledgable about (retired AA).
As a broad statement, I think the big 3 are all about the same. Anecdotally I've heard more positive statements about Delta, however no personal experiences myself. The only time I flew non-AA was years ago with Alaska and that was a pleasant one-off experience.
As another broad statement, on any given day any airline can absolutely suck given the wrong set of circumstances, many of which are beyond their control. For every passenger getting off an AA flight saying they'll never fly on AA again, there's another one getting on swearing they'll never fly on United again. The one airline I would avoid like the plague is Spirit simply because I've heard nothing but negative comments and no one has ever said they liked the experience. For years Southwest was the darling of friendly outliers, but with Herb Kelleher gone the culture there sucks the same as all the other unimpressive lines and they sure didn't win any friends last Christmas.
On the other hand, many things that disrupt a schedule can be avoided and it often comes down to who is working the problem for that flight or at that airport. As a crew member I was always aggressively proactive trying to find creative solutions but not everyone is. One last broad statement - the larger an airline is the more resources at their disposal to address an issue, and if it's an operational hub where the problem occurs, the higher the likelihood of filling in service gaps.
The biggest problem I've seen Domestically is people using travel websites to book their own travel and tripping over dollars to pick up dimes. The cheapest fare is not always going to serve you well. With these tedious disclaimers out of the way, I'd suggest the following guidelines:
- If given the option, always always always always always always choose a direct flight over a connecting flight regardless of cost. Did I mention always?
- If you absolutely must connect to another flight, if possible allow at least a two hour connection time. Travel apps will often suggest minimal connection times of less than an hour and it's just begging for trouble.
- Never never never never never book a connection from one airline to a different airline unless there is absolutely no other choice. Even then don't do it. Did I mention never?
- Even if you're traveling round-trip, I personally would make a different reservation for each direction. It will probably be the same price and it keeps things cleaner and more nimble if one of the trips needs to be adjusted.
- With multiple departure times for a given city pair, I'd suggest taking the earliest flight for the obvious and very real potential for problems that snowball into the remaining day's schedule. Also if the schedule does go South, more options are available the earlier you've started.
- When things go well, which realistically is most of the time, it's relatively painless. It's when there's delays and cancellations that things get sketchy real fast. I am pretty unhappy with the way AA has chosen to handle that - I don't think they are quick enough to allocate manpower to address schedule meltdowns, however every airline has their time on the hot seat so maybe they all suck at it.
- Sometimes the airlines and employees are as frustrated as the customers trying to make a broken industry work. E.g. at O'Hare (and I believe most airports) the wheelchairs are contracted out by the airport and at ORD they are spotty at best. Similar situations exist with the catering services.
Also, if for example you're flying in or out of New York airspace, ARTCC there is NOTORIOUS for throwing schedules into total disarray by starting and stopping ground delay programs on a whim for a single drop of rain and this often makes it impossible to decide when to board a flight during a ground delay, what is the likelihood of a crew going illegal, the list goes on and on about the frustration of trying to game a totally unreliable information source from New York airspace controllers.
BTW, when gate agents make PA's about the reason for a delay, they often don't know what they're talking about. They're not trying to mislead people (usually) but they often don't understand the mechanisms driving the delays or are simply flat out misinformed themselves. And those revised departure times posted on the status screens? Uggg... if the delay is due to an issued ATC "wheels-up" time then there's probably some actual math involved, but often times it's just some random departure time someone made up because they have no clue when the delay will actually be resolved, so they keep rolling it over and over and over (suspiciously in convenient 1/2 hour or 1 hour increments) just to put up a time that is IN THE FUTURE.
I could go on and on I guess, but the last piece of advice is pretty obvious - with some nuances. If you can avoid checking luggage, bring everything in a carry-on. But of course be smart about it - if you're on a long trip with a lot of stuff just check the bags at the ticket counter. Make sure all carry-ons are a reasonable size and know that it limits the toiletries you can pack (9-1-1 TSA liquid policy).
However, if you're not in an early boarding group, most flights are full so plan on having to gate-check your bags anyway. It might be worth it to just pay a few bucks to be in an earlier boarding group to snag some overhead bin space.
Here's the gotcha on connecting flights (at least this is how it works on AA): for a mainline flight, unless it has a pink tag like they use for strollers or critical personal items, that gate checked bag will go to baggage claim ... somewhere...
On a connecting mainline flight it SHOULD be gate checked all the way to your final destination, but wow, I wouldn't count on it. In that case better off checking it before going through TSA screening.
On the other hand, if it's a regional affiliate flight (i.e. not mainline AA but using American Connection or American Eagle livery) they should bring a gate checked bag to the jet bridge assuming the destination isn't using a hardstand parking spot. In that case, if it were me I'd ask the agent to only gate check it to the connection city rather than the final destination.
Good luck. Hope this separated some of the fact from fiction about why sometimes airlines seem to suck vs when they actually do suck. As a former airline employee, I'd rather take the train any day!
I expect it will be mostly city visits and train rides, as usual, but just less rushing around, and maybe "upgrade" to Motel 6 instead of hostels. 
