Originally Posted by
pinniped
MCI+2000 is effectively a contiguous-48-states (plus most of Canada) search.
I tested it out: MCI+2000 to LON, one-week stay, all of July. (I figure this whole idea of using other airports is mainly useful when DTW-LHR fares are likely to be very high.)
The query returned results in around 30 seconds, with YYZ being the leading contender with fares in the $700-800 R/T range on Air Transat. AC metal was a little bit more expensive, but not much.
FWIW, ITA appears smart enough to not query *every* tiny airport in the United States and Canada when you do a +2,000 mile search...just the ones that kind of make sense.
Good news for you is that YYZ might actually be a decent option if your actual start point is Detroit.
The MCI starting point is a good idea. I will try that.
And as much searching as I do, you are right....YYZ is almost always the best option for lowest fare. I have made the drive up Hwy 401 more than once to fly from Pearson.