To those in the know:
Why do many of the DC-9 flight numbers through DTW have an "equipment change"?

As an example today's flight 1402 from BNA-DTW-IAD has an equipment change along with the nasty A9 to A64 schlep. It seems that most of the DC-9 flights to/from the DC area do this ... and perhaps other places as well.

Why not just keep the same DC-9 for the flight numer? Or why not just use different flight numbers ... one for each aircraft?

TIA

IMO you might as well ask why birds evolved to fly and pigs didn't.
My best guess is that another aircraft uses that leg of the flight in better efficiency (time wise) than the other one.

I pulled up that flight to see why there might have been a shift in aircraft...it looks like there was a maintenance delay out of BNA? There are a multitude of reasons why aircraft swaps occur, and I don't have an explanation for all of them.
A dispatcher would have better insight into why certain aircraft get assigned to certain flights. A DC-9 with -7 or -9 engines might not work in/out of say Midway on a certain day due to temp,winds, etc. If you had an aircraft with -9 engines out of BNA, they would swap to an aircraft with -15 or -17 engines continuing on to an airport that might have performance limits/heavy loads/long legs(heavy), etc.
A marketing rep would be able to explain why a flight might be a DC-9-30 (100 seats) on one leg and a DC-9-50 (125 seats) on the next leg.
A maintenance rep would tell you that you can stay on the aircraft you brought in and wait two hours for the generator to be replaced, or schlep down the concourse to a completely healthy jet that is up and ready.
Aircrew get to do the same dance you do....it's called the "Bag Drag" and we prefer to stay on the same jet all day long too if possible...unless I'm going into Midway...then I'll happily trade that -7 for a -17 any day.
This phenom isn't unique to the DC-9 fleet, nor Northwest for that matter. It's fairly common at most airlines that are marrying up capacity, performance, maintenance, etc. Hope I answered part of your question....thanks for flying NWA!

Equipment assignments are done to minimize operating cost.

Direct flights are just marketing ploy. e.g. NW has a "direct" flight between JFK and HKG, with a "stopover" in NRT. Note that CX also has "direct" flight service too; however, they've been wanting to do non-stop service.

I once flew ORD-MNL "via" NRT on NW flight 3 about 15 years ago. The funniest thing: I missed the continuing flight because of a mechanical delay.

Note that by chosing "direct" flights, you only get the mileage A->C vs. mileage from A->B->C.

If I ever come across an option for a direct flight, I'd break it up into two segments.

- Pat

I have no problem with flights that experience a change of equipment due to mechanical needs or because of changes in demand during the course of a day.

What I find objectionable is the allegedly direct flight A-B-C where the plan all the way along is to utilize a different aircraft from A-B than B-C. It is just plain or is it "plane" deceptive.

I think it's mainly because of marketing. For example, AA may have a flight at the same time from BNA to ORD with a connection to IAD. If NW however markets a direct BNA-IAD flight with a stopover in DTW, it will go to the top of the heap of the computer display in a travel agency. That was what a travel agent explained to me some years ago. I don't know if this still holds true and I also don't know if the same theory applies to internet sites such as Orbitz et. al., but it made sense when it was explained to me at the time. Now as far as the plane changes are concerned, I think years ago they tried to keep the same aircraft on the entire itinerary, but I believe now the name of the game is matching equipment to demand.

Thanks for all the replys.

The flight and day combo I mentioned was just an example ... the maint. delay was coincidence. This is a regular occurance on routes to/from Washington-Dulles. And I've noted it's a DC-9-30 both into and out of DTW.

The engine thing might be it ... but Dulles has 10k+ foot runways so there's not a performance problem there. Maybe Bay City MI has short runways??

I'm used to the direct "marketing" from Delta ... but NW definitely has more "equip changes" in DTW than I ever saw DL have in ATL.

Maybe there's an ops person who could (anonymously, of course) chime in. Or maybe I should be paging B747-347 ...

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Leo showed us his new loyalty program so we showed him ours ...
2003 DL spend = $0
2003 NW spend = $21.4k and increasing