Crazy as it seems, I drove from Cleveland, Ohio, all the way up to DTW last Saturday just to spot planes.
Someone at planespotting.com had recommended parking on the long-term Deck and that's where I headed first. Unfortunately it was 85-deg-F and I couldn't bear to stand up on top for more than 1/2 hour.
I took a good look around the airport after I went in and guzzled two bottles of orange juice. There is a relatively good ground transportation/shuttle system which allows anyone to get a ride from one part of the airport to another. The only drawback is that you have to go to certain places along the exterior of the building -- you can't just wave down the vans. On the other hand, that provides for smoother traffic.
My initial view of DTW was from that of a passenger and then my experience was limited to the middle and end portions of Concourse D. At the time I felt it was a very dark, cramped airport with a gross lack of seating and free space. Well, I found a little more space, in the main buildings connecting the different concourses. However, I'm sure a lot of passengers won't have enough time to sit down and enjoy the concession areas like I did.
Back to the Deck Parking area -- if you go all the way to the top (Level 6, don't miss it or there's no way back up the "Super Ramp") and park in Section 6e (as far as you can go from the Super Ramp), you get a good view of departing traffic on Rwys 3C/3R. You also can see arriving traffic on Rwy 27R. Rwy 27L is too far south of the Deck and arriving traffic is so far away that you need binoculars to appreciate it. By comparison, the departing traffic is either at or just beyond "wheels up." Unfortunately the Super Ramp blocks the view of Rwy 3L.
Since I was there only one day and the weather didn't change, I can't tell you about what Rwys 24C/L would have looked like, but since the ends are parallel to the Deck, it would probably be a great view.
While I was in the airport I spoke to a few different "green vest" customer service agents as well as three different shuttle drivers. One of the drivers, a woman who says she brings her kids to the airport to watch planes quite frequently, told me that the Green Lot would be a better place to park -- not only because it is slightly cheaper, but it is directly adjacent to Rwy 24C/3C. Come to think of it, with the shuttle service, you could park there and still go up on top of the Deck.
I also spent about an hour in the Berry International Arrivals Terminal. All of the international and charter flights arrive in that terminal for customs clearance. Most of those same carriers also reboard their aircraft in the same location; however, KLM and Northwest have the option of being towed next door to Concourse F. I saw a KLM 747-200(?) and a Northwest DC-10 towed over while I sat there. Unfortunately the view of Runway 3L/24R (12,000' and therefore the choice of the jumbo jets) is partially blocked so I only saw the jets just after "wheels up." IF the traffic was going in the opposite direction you would only be able to see the very beginning of the takeoff roll. The beginning of Runway 24R is south of the terminal.
My intention in making the trip to DTW was to see the larger jets that don't come in to CLE. I fulfilled that "mission" with two 747-400s (Northwest and British Airways), a 747-100 (Northwest), a 747-200 (KLM), an Airbus A-340-300 (Lufthansa), and multiple DC-10s (Northwest). I also saw lots of 757s (Northwest) and a Delta 767.
Of course there were lots of other aircraft as well. For the first time in memory I saw USAirways DC-9s (still in the old paint scheme). I'm glad I got to see them before they are all retired. I also got to learn how toidentify the Airbus 319/320 by engine sound (I'm a musician). It was also nice to see so many 727s.
All in all, it was worth the long drive. Although Northwest dominates DTW, there was enough variety of aircraft (including different series) to keep me quite fascinated. I'll have to plan another trip, hopefully a longer one which will include side trips to Willow Run and Detroit City Airports!