Two Examples
Three years ago, I went to opening day at Celtic Park in Glasgow on a SkyMiles ticket in J using the following open jaw: IAD-DTW-AMS, returning EDI-CDG-IAD (the outbound was on Northwest metal, EDI-CDG was on AF's commuter partner CityJet, and then an AF 777 back to Washington). I fooled around on line for over an hour until I figured out an itinerary that I could get for as close to the minimum as I could get (I think it was 95k SMs). I took the overnight ferry from Ijmuiden, at the mouth of the river Ij, to North Shields, east of Newcastle near the mouth of the river Tyne, and then train to Glasgow, with a stop at Berwick-upon-Tweed to take a public bus to Holy Island (accessible only at low tide) to see Lindisfarne. It was a great little trip.
Two years ago I went on seven days' advance booking to see Celtic; I bought the cheapest coach ticket, at about $650 AI, and got the following routing:
DCA-DTW-AMS-GLA; and on the return, DUB-ATL-DCA. Actually got an op-up DUB-ATL, and the domestic legs got upgraded. This was between the time that the merger was consummated and the time that the FAA granted DL one consolidated certification for both fleets, so technically I was on a "DL operated by NW" trip eastbound, KLM Cityhopper to GLA, and then DL metal coming home. After Glasgow, I toured northwest England with a 4 day rail rover ticket, and then took the overnight ferry from Birkenhead (opposite Liverpool on the Mersey) to Dublin.