The difference is mind-boggling in some cases. On one trip in 2019 I had the following coach fair choices for SFO - Moscow return trip tickets booked 3 weeks prior to departure.

* UA or Lufthansa round trip (single carrier) $3K

* UA round trip SFO - Paris + Aeroflot round trip Paris - Moscow: $1K

No amount of search could reduce the gap. I went with the second option. The gap is even bigger if you have a route with multiple segments.

https://www.airtreks.com/ will do this for you with a person. phenomenal service.

To anyone from airtreks, I love you so much!

Yeah this strategy is good, but you need to allow a long layover like 6 hours if you have to go through immigration and change airports for the connection which happens pretty often with ryanair and ezjet. It’s a big pain, but it does save money.

If you're booking each leg with different carrier, I find it best to pay the little extra with kiwi.com and they give you guarantee for the connection. I missed connection twice and they always got me on the next flight to the destination for free.

in my ideal world the software ITA wrote for airlines and is now owned by Google would be in the hands of consumers and the airlines could have adapted to shifts in demand probably without the need for abrupt cessation of services and human fatigue on industry employees caused when route optimisation analysis tempts executives with what I suspect are ultimately fictitious net present savings.