I imagine there's probably two different basic schools of thought when you are the commander of an alien spacecraft:**
1) To Fly Your Ship Over Rural Areas
PROS: There are less people to spot you
CONS: There aren't very many interesting things to look at in rural areas (which probably results in lots of cows being mutilated out of boredom) and you are more visible because of the reduced lights.
2) To Fly Your Ship Over Urban Areas
PROS: More interesting things to look at and investigate, your ship is less visible because of all the lights and the chance to blend in with airplanes
CONS: There are more people to spot you, you may get in the way of airplanes
After examining the evidence and weighing the pros and cons carefully, it's beyond me why most commanders of alien spaceships opt to fly their ships over rural areas. Or maybe more UFOs are spotted in rural areas, when really they are more prevelant in city areas, we just don't notice them?
Personally, I know that if I was the commander of an alien spacecraft, it'd be a pretty tough call to make.
*Speaking of "Country Mouse, City Mouse" we have mice in our house. Just thought I'd let y'all know.
**I think the most disturbing thing about this post is that I just woke up, and this is the first thing that popped into my head and perplexed me. It's especially absurd considering I'm not an alien fantatic, nor do I ever think about extraterrestrial life, well, ever. I don't really believe in aliens, although I think it would be ridiculous to presume we are the only life in the universe. (On that note, does the microbiotic bacteria that they found on Mars, or wherever they found it, count as an alien life form? I think it does.)
Although, I did see a UFO once. But that's another story.