May 10, 2011

Crossing Traffic

It always strikes me as odd how the same airline will file different routes to the same place, often causing their aircraft to cross paths. The most common example that I have noticed are the BDL/ALB/BTV flights going to MSP. On more than one instance, the BDL (most south) flight ends up taking a routing north of Lake Ontario, the ALB (middle) flight takes a more direct (and most often flown) route over Waterloo (the one in Canada, YWT), and the BTV (most northern departure point) will head southwest over Buffalo and Milwaukee. Being oddly curious about things that don't really matter, I have wondered which flight got there first. Here are two recent examples where I have remembered to keep a copy of the strips so I could look them up on the fabulous (thanks flightaware!) after my shift.


Two Delta flights departed Albany and Bradley bound for Atlanta on a Friday afternoon. There were some thunderstorms around, but there wasn't an official weather reroute in effect at the time.

DAL1913 departed Bradley (BDL) first, at 1:09pm, with a flight plan filed over upstate NY to central PA and south over West Virginia. DAL1023 departed Albany (ALB) a few minutes later at 1:12pm flight planed over NJ, eastern PA, overhead DC and then over the Carolinas. Both flights usually fly the eastern route that DAL1023 flew. Both flights' targets merged over the ACOVE intersection just south of ALB, as you see below, and the race was on. DAL1913 was about 2000 feet higher than the DAL1023.

The first flight to arrive was DAL1023, which flew the normal routing to Atlanta (and appears to have deviated around some storms over Maryland), at 3:26pm. Two minutes in-trail was DAL1913, arriving one or two planes back in sequence at 3:28pm.


A few days ago, I was sitting in the D-side at Utica and we had two E-170s tied over SYR, both requesting FL360. RPA3305 had departed Montreal (YUL) at 7:47am and RPA3124 who departed Ottawa (YOW) at 7:53am, both bound for Charlotte (CLT). My R-side gave the Ottawa departure, who was a few thousand feet lower in the climb, a vector to the east behind the Montreal departure.

The Montreal departure had filed the normal routing over central PA, West Virginia and and then onto the CLT arrival from the northwest. The Ottawa departure filed Syracuse direct to Roanoke, VA for a different arrival route from the northeast. As strange as this was, it was a Saturday morning, so we simply vectored the Ottawa flight east a little and gave him direct Roanoke, which allowed both flights minimal delay up to FL360 once we had crossed them out and established them on perfectly parallel routes.

Something happened half way to CLT, though. The Montreal departure, who was now west of the Ottawa departure, got massively vectored back east and put well behind the Ottawa departure on the arrival route from the northeast. After all was said and done, RPA3124 (YOW) arrived first at 9:48am, and RPA3305 (YUL) arrived at 9:55am. I'm not sure what happened, as this reroute occurred well beyond my airspace, but I can only assume the YUL departure would have arrived first if nothing had been done, since the flight arrived only 7 minutes behind the other despite the extensive delay vectors.

Till next time...



getjets said...

Great Post!!!!!!!!!!
I sent an e-mail...but just wanted to give a big 'thumbs up' on the tail end of your post!!!!!!!
I may be wrong, were those flights on "Good Friday"??
maybe something with the holiday....
a whole new meaning to 'two steps step back....or whatever..
Take care,

getjets said...

Hey Mr. DM....
Referencing your March 8,2011 post "Missing my Train"....
Thanks so much for posting your pics..especially the one of the "Old TWA Terminal!!!!!!!!!!!
Have you ever seen the program, when they moved the terminal building, on TV a while back..very interesting...
I listen to JFK...ATC... almost everyday, and know their voices, One in particular, who says "GOOD FLIGHT, GREAT DAY"!!!with just about every departure....
I will have to check out BOSTON, ATC now....!!!;)))))))

Ya'll are so cool, and I mean that seriously!!!
It is Appreciated!
misstwa(because I really do miss TWA)

Dan in ALB said...

I am in no way involved in the airline field, but my guess that the different routing are attributed to different dispatchers and individual pilots' preferences.

Just a guess.

Anonymous said...

One possibility on the MSP flights is BDL is cleared/filed CTR..CAM, so the part of the route that the flight planning software can play with starts north of ALB.

For any of the routes, different aircraft types, or different passenger loads on the same type, lead to different cruise altitudes which can have different winds aloft and turbulence. Different altitude capabilities from nearby airports to the same destination could make a longer route cheaper, at least for flight planning purposes.

One more factor for westbounds, although it's more likely from ZNY airports. Say BTV-MSP is already leaning toward a more southerly route today than ALB-MSP and BDL-MSP. A route such as BTV..BUF..JLGON..BAE..MSP avoids Canadian overflight charges, which could make it the winner. It's all about $$$.

Thanks for the great blog.