On those rare occasions when a north wind blows, we know to pack up the kid and his toy airplane collection and race to DFW Airport's observation area, where he'll see jumbo jets--747s, A340s, 767s, L-1011s and DC-10s and the many smaller varieties--practically landing on top of him, and he'll watch the results of those tiny, precarious adjustments the pilot makes just a few feet from the end of the runway as he's coming in to land. (You'll also notice that it takes forever for those ancient 727s to get off the ground.) You probably didn't even know this "Founders Park" existed, with its panoramic view of the airport's east runways and piped-in control-tower chatter. But a few of us have found it, and it's perfectly suited for an outing with a plane-obsessed child (or adult). It's almost entirely fenced in, and it has picnic tables, litter-free grass and lookout binoculars (very blurry; we suggest you bring your own). Hey, and it's all free. To get there--DFW doesn't make it obvious--take the south entrance to the airport and follow the signs to the south shuttle parking area. Go past it and keep following the road until you reach an overpass. Turn left before the overpass, and you'll end up at the park. You can watch outside or in your car. It's best to come when there's a north wind, because the planes approach from the south and land right in front of you. Other times, you get a better view of the takeoff. (At press time, Founders Park had survived the new security measures at DFW and remained open.)