I just got an email from DL announcing a two day sale of (apparently) Z class RTs from the USA to London for the summer. Minimum stay is seven days, maximum three months, but the effective travel dates are June 1 to August 10 for outbound travel. Advanced purchase requirement is 21 days. Some blackout dates by route.

For MSP, I'm seeing RT fares of $2821 for most routings on random dates, including VS operated flights sold as DL codeshares, with $2844 for CDG connections and $2849 for AMS connections on random dates. This compares to fares of about $4000 last summer.

What's curious about the email is that it lists blackout dates for MSP-LGW flights, but AFAIK all of the MSP service, including connections that appeared for random dates in June and July, uses LHR rather than LGW.