Thank you all for your input . My biggest concern is getting on a flight from Denver which is the last flight for the connection from MSP to LHR if there is some flight delay somewhere and that flight gets booked up with fare paying passengers I am stuck in Denver as the LHR flight leaves. so I think the better option is to leave on a earlier flight. flying out of ATL to LHR is also an option that we could look at although a few hours at Mall of America is very appealing.. again thank you all for your help and I will certainly let you know how it goes.