Favorite Airlines?

A lot of people use Aer Lingus to Ireland, although we personally flew United out of Detroit when we went. My favorite airlines overall is Air France. Next is Air Canada followed by United. Hopefully someone else can speak to Aer Lingus since they are the Irish airline. Good luck. You'll love Ireland!

I generally fly British Airways or United since they have decent connections from the nearby airport.

I used Aer Lingus in March of last year and it was fine. I paid a little over $600 roundtrip to fly coach from San Diego to Dublin via San Francisco, so I can't complain about price. It did feel pretty cramped on the plane and it was an almost 100% full flight both coming and going, so I wouldn't award it many points for comfort. (My last international flight before this one was to Sydney on Air New Zealand in 2000 and I didn't remember that one being this uncomfortable, but I know a lot of things have changed since then.) Staff was friendly and all legs of the flight were on time. Other options may or may not be better... I haven't used them, so I can't compare.

(The part of the trip between San Diego and San Francisco was on United. Only the part between SF and Dublin was on Aer Lingus.)

Our first trip to Europe from Seattle was on Condor and it was comfortable and the service was good. Our second trip was on Air Canada (we live near Seattle but flew out of Vancouver BC because the options and price were much better). Service and comfort were excellent. This time we are going to Ireland on British Airways and looking forward to it. Have heard good reviews from friends who flew BA. For the dates and times we wanted, BA had the best price and schedule.

Have fun!

I would also consider which airlines offer a "comfort plus", "economy comfort", or "world traveler plus" option. I have found this can make a huge difference. I just flew "comfort plus" on Delta. There was 4 inches of extra legroom and I could stretch my legs completely out in front of me. More space=more sleep and less pain for me. There are dedicated overhead bins for comfort plus so no issues with fitting the carryons in the bins. You get priority boarding and since you are right behind business, you are off the plane fairly rapidly.

Consider the level of services offered as well as brand/price when shopping for airlines.

I would avoid a code share (more than one airline - partner airlines) it will turn out to be more expensive in the end (different rules for different airlines) and more complicated when the airline changes flights or times (hours on the phone).

If you go through LHR make sure you have more than 2 hours when switching planes. Moving between terminals means you go though security again. With a flight delay it will was extremely stressful and required a jog to make the flight connection.

I would highly recomend Premium Economy (American) or similar World Traveler Plus (British Airways). It is worth every penny if you can afford it. We flew 12 hours each way and this made it much easier since we are tall humans and don't fit in regular economy seats any more.

I like Aer Lingus a lot, but if you have a Known Traveler Number for TSA Pre-check, they are not an airline that participates in that program, so you cannot go through Pre-check if you are flying with them unless you are doing a combined flight with another airline. I know they partner with United and JetBlue. When we went in December, we used United to get to Heathrow and then Aer Lingus from there to Dublin, and that went fine. But on our next flight, it was Aer Lingus only, and no pre-check.

Thank you everyone for your replies! We ended up booking our flight on Delta, and we did go economy plus. So hopefully we'll be comfortable during the flight. I can't wait to see Ireland!