Help in understanding flight options

Sometimes airlines publish on-time performance of a particular route when you go to buy the ticket. However, it's not consistent. Some do and some don't, and it's hard to make and apples-to-apples comparison. Also, you only listed the connecting airports, not the entire itinerary (origin and destination airport)...all three are important in terms of whether the flight is likely to get in on time. It also depends on a host of other factors like weather. All you can do is allow plenty of time leeway at the connection and avoid airports that have chronic issues with delays, particularly due to extreme weather conditions.

In addition to the points made above by Agnes (all correct and good points), I'll add...

What time of year, what time of day? Can make a big difference (eg: potential snowstorms in Salt lake City during the winter, fog can cause delays in SFO throughout much of the year, but that's generally more of an issue during mornings than later in the day).

That said, none of these three airports are notorious for horrible delays. Of the three, SFO + fog is probably the most delay-prone. But I'd still rather connect there than most airports further east (for a long list of reasons).

All of those airlines are pretty reliable -- as reliable as any other. Things that are most likely to disrupt your trip are not specific to any of these airlines (eg airport melt-downs or widespread bad weather).

Don't overthink this too much. Any of the options you have listed would be fine (all other considerations aside).

One thing that I would keep in mind: the amount of time that one needs to allow for a comfortable, drama-free, successful connection is now greater (at least it's longer for me than it was 2 years ago). The number of people who are traveling nowadays are very high, and show no signs of declining -- this is the new normal (until it isn't).

Recall last summer (during peak travel demand) we saw lots of "airport meltdowns" which resulted in lots of travel drama. Going forward, it's a good idea to give yourself a bit more time to make connections than you would have a few years ago. Exactly how much extra time depends on details you have not provided. Post more specifics and folks here can tell you how comfortable they would be with that connection.

It would help to know sour starting airport. It looks like Boise but there must be other towns with similar options. It appears from other posts that your trip is in May, is that correct?

Of those airlines, I would choose either the Virgin Atlantic flight (with Delta Skywest to Salt lake and VA from there) or Delta through Seattle. Both Delta and Virgin are well- regarded airlines and both have their fans.

Salt Lake is a smaller, easier airport to negotiate, all things being equal, but you also need to consider what alternate flights might be available for you at each airport if your short flight to that airport arrives to late to connect with the long flight.

I don’t like United so won’t comment, other than to say my very well-traveled son who lives in San Francisco avoids SFO when he can, due to flights delayed by fog or wind. He also favors Virgin Atlantic over other airlines for flights to Europe, so for that he is willing to use SFO.

Thanks for all the comments so far. Of course I should have given more info.
The routes are from Medford Oregon and destination is London.
Our departure is around May 1st returning a few weeks later.

Length of the connections in each city?

I can assure you, Virgin Atlantic ain't flying out of Medford (a lovely little regional airport, by the way). Whether you head for Seattle or Salt Lake first, that hop will be on a partner (eg Skywest, though will probably be painted in Delta colors); the long flight to LHR could be on either Delta or Virgin Atlantic (they codeshare many flights). Same if you go via Seattle.

A lot of people love to hate on United. Personally, I think United is generally a solid, reliable airline that does a good job on most things, most of the time (same as any other big, domestic, legacy airline). I have noticed United has improved their customer service a LOT since they had a few infamous PR disasters in recent years (one involving guitars, one involving a very unhappy doctor). I fly United to Europe often and I'm quite happy on them (and I'm fairly picky about my flights).

Given what you've stated so far, I'd make my choice based on the relative convenience of the connections and the schedule, and perhaps most of all (and not yet mentioned)...the seat dimensions for the long flight to LHR. All seats are not the same, some are more/less comfortable than others. If it were me choosing, I'd note the seat details as a high priority (you need to look at the details for your specific seat on your specific flight, on the day you travel...not just compare the airlines generally). For me, that (seat comfort, or lack thereof) would be a deciding factor, though others may not care so much about that.

Excellent points by David. In addition to sear dimensions, you might also want to consider the seat configuration . If there are 2 of you traveling, you might prefer 2-x- 2 over 3-x-3 where you might have a stranger in the same row. And would you consider Premium Economy if it is better, snd at what extra cost?

I notice you haven’t mentioned the British Aieays optio, with Alaska Sitlines ( actually their partner Skywest) from Medford to Seattle and BA from there. Is it more expensive than Delta?

Iceland Air has a sale on that ends soon (tomorrow). I put SEA to London in for May 1st with a return a few weeks later and had a RT price of $783 regular coach. This is a good price. You would have to get yourself to Seattle, and it is a good idea to bring your own food/snacks on these flights. You do earn Alaska Air miles which would help with the next trip :)

Have you used Google Flights to research potential flight itineraries?

I haven't used Skyscanner in several years, so they might do the same thing, but one feature I really like about Google Flights is the ability to use their calendar (called Dates) option to compare prices for different departure and return days. Note that this only works for round trip flights. If you have the ability to be flexible, it's amazing how much money you can save by adjusting travel dates.

You can also do things like limit the number of stops, choose particular airlines or choose specific alliances.

And you can sign up to receive email updates for your itinerary options when prices change.

As to international departure airport, I've left from SLC and SEA. I prefer SEA because of the flight path and efficient way to get from local flights to international ones. SLC requires much more walking to get from local arrivals to international departures.

I'd be VERY sceptical of any RT Medford-->SEA or SLC flight that gives you only an hour or less to change planes for London -- even if you do carry-on only. It would be worth it to me to explore multi-city or 2 RT options to avoid that if necessary.

For example, you could create a multi-city itinerary (MFR-->SEA-->LHR, LHR-->SEA-->MFR) to see flight options with more transfer time at SEA and have all flights on the same ticket. OR you could separate the MFR-->SEA, SEA-->MFR and SEA-->LHR, LHR-->SEA segments into 2 separate RT flights.

There are advantages and disadvantages to both those work arounds. Prices may be better or worse.

Today I saw RT MFR-->SEA-->MFR for most dates in May at $158 on Delta/Skywest and $198 on Alaska.

I also saw nonstop RT SEA-->LHR-->SEA for $727 on American/British, $807 on Delta/Virgin. Note that shifting the return date by one day dropped those prices to $677 and $757 respectively.

I think that none of the disadvantages is as great as the possibility of missing the nonstop flight to Europe because of some MFR to SEA or SLC kerfuffle.

S balance of bedtvprice and best schedule is all that matters.

VA does not fly to SLC so that itinerary is also all Delta. Also, would you trust an airline that puts Las Vegas in central Oregon? https://flywith.virginatlantic.com/gb/en/destinations.html

Tom_MN, that map is funny and sad at the same time! And Virgin Atlantic’s not quite as far off with their positioning of Seattle, but they’ve got it on the wrong side of Puget Sound, about where Sequim, WA actually sits.

Heck, the Virgin Atlantic route map also has Atlanta somewhere around Arkansas, not in Georgia. Still south of the Mason Dixon Line, but still . . .

Thank you all for this excellent advise. I will be getting on the computer later today and seeing hopefully more clearly the options available.
Yesterday I saw a good option through SLC but one leg, back from London to SLC, said it was not selling more seats at the slightly more expensive option I chose, and therefore there were not any more of the two-seats-only in the row option. I would like to get that option somehow so will look today. Also will check seat size. I think they said yesterday something like 17 1/2 - 18 inches which I guess is not a lot of space.
The layover time was 4 hours. This felt better to me then anything less than 2 hours. I am just cautious that way due to previous delays.

We bought tickets! This raises the excitement level. They are with Delta. We bought tickets through SLC with a 4 1/2 hour layover and coming back through SEA with a 3 1/2 hour layover. Other options were an hour or even less of a layover and we didn’t want that.
Anyone know of quiet places to hang out for a few hours in these two airports, to relax for a while?

Also, we paid extra for fully refundable (200.00 each) and the comfort plus level (150.00 each) which we have never done before. Always did basic economy before.

SeaTac has a nice new area with gates that aren’t being used yet, so it is very quiet, but also nice and bright, with lots of windows and natural light.

After arriving at the international terminal and passing through immigration and customs, make your way to the main terminal, and walk down Concourse D. You will see a large hallway on the right, signed for gates D21-26. That is the area you want. Lots of options for sitting or walking laps. I think there is a Peet’s Coffee right opposite the hallway entrance if you want coffee or a snack, and more food options down the regular D concourse, or the adjacent C Concourse. I like Hachi-ko near the end of C Concourse for decent Asian-fusion food.

Thanks Lola, that sounds like the exact kind of place we would want to walk and sit in for a few hours.