If you want a cheap flight from Minneapolis-St Paul to London, you've got two airlines to choose from.
Make sure you use the search options above to search for flights to other airports in London, not just London Gatwick. The more options you look at, the better your chance of finding a cheap deal. Just so you know, the flight typically takes 12 hrs 45 mins.
If you're planning on going to London during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.