What's the "correct" mileage calculation?
 

I was on a NW flight that was supposed to be direct from PHL to ORD. We flew from PHL to DTW, changed aircraft and departed from a different gate from the arrival gate but the flight had the same flight number. The same thing happened for the return flights. When I checked my mileage, I received mileage for direct flight from PHL-ORD (about 637?) instead of 2x500 miles for PHL-DTW-ORD. When I called NW to check on this, the person I spoke to said that it is considered direct flight because the flight number was the same rgardless that we changed aircraft and gate. Has anyone experienced this and is this "correct"? If yes, can someone direct me to where it is written?

Yes, this is correct. A direct flight (one that may make a stop but all segments share the same flight number) will only be granted the mileage from boarding point to the point where you end your travel or the flight number changes again.

It's written in the terms and conditions here:
http://www.nwa.com/features/earnfltmilestc/

I have been on NW 1719 from Clt - MKE with a stop in DTW, 651 miles credited for entire flight, same flight number, was considered a direct flight. My bad. I wasn't really paying attention to the flights when booked, I now make sure my DTW flight/connection has a different number, I do not mind the layover (unless it is the last flight of the day). You will also get credit for 1 elite qualifying segment, not 2. :(

Thanks for the info
 

Thanks TheMoose and Crazy Dave for the info. I will now pay attention to the flight numbers when making my NW reservations since most of my flights from PHL are connecting flights via DTW, MEM or MSP. I just checked and the same thing happened with my flight on 8/27 from PHL to SIN via MSP and NRT. The flight was considered direct flight from MSP to SIN. Glad I found out before booking my next flight (PHL-BKK) which also connects via NRT.

Doesn't matter when you found out - SIN has the continuing flight numbers and BKK does not.

Which sucks, because the wife and I are trying to do a keep-the-elite-status trip to southeast asia and would like to go to SIN, but due to the loss of miles on the direct flight number, are probably going to go elsewhere.

Here's my question - if we force an overnight in Japan, will that 'break' the flight into two segments?

And scratch that - looks like NRT-SIN is 1x daily so it'd violate the 24-hour international routing limit.

Not complaining, but this just doesn't make any sense!
 

So I was on a flight from MSP-ORD (NW186) and a flight ORD-DTW (NW534) where I got off the plane (at ORD), and then reboarded the same exact plane. Because it was a different flight number, I received 1000 miles, 2 segments. The ORD-DTW flight was actually continuing on to LGA (NW534), but there was an aircraft change. We arrived at A66, and LGA flight left out of A18 (in Detroit). I feel for you travelers that get shortchanged and lose miles on this deal. I don't understand the meaning of direct if you have to change planes (and haul butt all the way to the other end of the terminal).

it's an industry thing and NWA isn't alone doing it but yes I agree and avoid direct flights as often as possible