How close together are the two one ways? I'd be a lot more comfortable with two one ways separated by a week than two on consecutive days.

We booked one way tickets from CLE to Los Cabos last year, both ways on Delta. Had no real issues. We did get questioned about having a return flight when going into Mexico. When I told then we were flying back on Delta they had no issue. Said be prepared to show if they ask in Mexico.

Glad to see it's usually okay to do this, since it's my SOP for my 5-7 week, retirement overseas journeys. I book the departing flight, then work on the itinerary and timeline, and finally book the return flight after I know where my travels will take me (usually it's open-jaw anyway.)

I bought a OW ticket to Manila several years ago. At check-in in BOS, I had to show proof of an onward flight out of the Philippines.

Depending on where you are going overseas, this can be dramatically more expensive than a roundtrip booking. One-way's to-from EU destinations in particular. Most of the cheaper fares require a roundtrip booking.

Or course there is also the positive to two one ways that if you don't fly the first part for some reason, the second won't be automatically cancelled.

Basic economy available in one direction but at a fare that can't be combined with a main cabin fare on the return, so to price as a RT you have to pay the main cabin fare in both directions. As two one ways, you'd pay BE + main cabin.

Point taken. In fact, I don't believe you can ever combine a BE fare with a non-BE fare on a single roundtrip booking due to BE fare restrictions. On the other hand, if you are purchasing BE in one direction and MC in the other, it's no longer really the same exact product as two MC fares.

+1 I've been buying 2 one-ways for years on routes where they are price-equivalent to a round trip. Needing to make a change to / cancelling or otherwise not flying one segment doesn't ruin the whole ticket. In terms of change fees, I usually only need to make a change to one segment (not both), and booking a fresh one-way can sometimes be less than $200. This happens a lot when tacking personal travel on before/after work trips. Have never had an issue needing to get trip in vain or getting IRROPS help where warranted.

The LAX-SLC market seems to be one of those one-offs where a simple A-B-A round trip is cheaper than the sum of the one-way pricing. I haven't looked into the fare tables to see exactly what's causing, and if it's seasonal, but an example

LAX-SLC Jan 17 - Jan 19
DL2658 Jan 17
DL 1348 Jan 19

Roundtrip price for Main cabin: $380.80
DL 2658 - $215.40
DL1348 - $200.40
For a total of $415.80 or a $35 premium to the roundtrip ticket.

That said however, I almost always book one-ways. The biggest 'benefit' is that I don't have to fly the outbound for the 'return' ticket to be valid. Very useful when I may be traveling A-B-A but later find out I actually need to come directly from a 3rd city where it's cheaper to just fly C-B and then take my original B-A rather than pay a change fee + have the whole C-B-A be repriced at the (likely) higher price.

It's really not that complicated. Look at a market where there is a large LCC presence (like LAX with WN, SEA with AS, or BOS with B6) and the routes they fly non-stop. These LCC's (okay, AS is technically a legacy) all price roundtrip's as a combination of one-way's and don't have any fares which require a roundtrip purchase and DL tends to match these. Do an Expert Flyer fare search and you will see DL has a small handful of fares on LAX-SLC that require a roundtrip purchase, but the vast majority are WN fare matches (as WN also flies this route non-stop) and don't require a round-trip purchase. Compare that with an Expert Flyer search on LAX-DTW (where there are no LCC's competing non-stop -- only pipsqueak ULCC NK) and you will see DL has a ton of fares which require roundtrip purchases.

So yes, they would be considered a "one-off" in LAX (particularly if you are only flying to major markets where LCC's compete non-stop). But in a market like DTW, where the LCC's have a limited presence, roundtrip fares on DL are present on the vast majority of routes. About the only DL routes out of the DTW that have no fares with a roundtrip purchase requirement are BWI, ORD, MDW, DEN, SEA, and STL. Even BOS (B6) and BNA (WN) have a handful of fares requiring roundtrip purchase.

Ah I feel dumb. The part of your post I quoted I completely mis-read. Don't know how, but I read that you were saying that the sum of two one ways should not cost more than a roundtrip (clearly not what you said).