This might be a little bit random, but I've noticed some flight patterns at both DCA and PHL today that I've never seen before. I'll start with DCA: As background, I live in Old Town Alexandria, so I'm quite familiair with operations at DCA. Today, they've been taking off to the south. Normally when this happens, all the aircraft using the primary runway will essentially fly straight down the Potomac during their initial climb, not really turning until after they've passed I-495 (that's my rough estimate, anyway). Well today, I was walking to the metro to get to the airport, and I noticed a US Airways plane turning hard right up ahead of me, so it was pretty close to the airport. The flight path was probably a good 45 or 50 degrees west of the normal flight path when taking off to the south, and he continued to turn harder than that. So I immediately thought it must have been a go around, with the plane turning right to get back into the landing pattern from the north. However, two minutes later, a Delta MD-88 did the exact same thing. So I thought that was really weird...to go-rounds in a row?! But then three minutes later, a third plane did the same thing, so I knew it had to be something more than that. Then, once I got up on the metro platform, I could see other planes making equally hard lefthand turns shortly past the airport...it was like there was an invisible object in the sky straight ahead off the runway that they were trying to avoid. In fact, I actually was slightly concerned that something had happened at the end of the runway (until I arrived at the airport to see everything looked normal). When I finally took off a couple hours later, we had a normal, straight climb, so I don't know what was going on. Then, during our arrival to PHL, we were landing to the West, as is pretty common at PHL, and I looked out my window (I was on the right side of the plane) and I saw an Air Canada plane parallel with us! I quickly realized we were landing on 27L, while the AC flight was landing simultaneously on 27R. I'm now sitting here in terminal A watching this happen over and over again...planes landing essentially side-by-side at the same time. I've flown in and out of PHL a good bit in my life, but I've never seen a double approach like this. When landing in this direction, 27R always seems dedicated to arrivals, while 27L is totally dedicated to departures. Anyway, just thought I'd share--maybe someone else experience today as well and has thoughts?