Originally Posted by
flyerCO
The multicity search was changed a few years back to force fare breaks. I'm not sure the reasoning. You can call in (no fees for this with DL) and have agent book over the phone. Note if it's a valid connection but system search doesn't return it, not all agents know how to piece it together anymore. Ie i generally loke booking overnight connection at AMS. As long as under 24 hours, its a valid connection. However DL system will only return the options for aame day on most routes. Tp book the 23.59 connection, must call in and agent must put in flight by flight.
IIRC there can also be married segment availability issues for certain routings and/or segment choices. It can be a valid connection, but despite fare class availability on the individual segments, one can be forced to go to a higher fare class for the through fare. PreCovid-19, I often saw this on EU-AMS (overnight connection under 24 hours) AMS-USA trips.
These situations were easier to handle when delta.dumb offered the advanced search to pick a particular fare class or higher. It was also better when you could use multicity search to individually select segments that formed a legal connection and get through fare pricing.