You got it, I'm at 49999 EQMs, 1 teeny mile short of requalifying for GE. I am not worried about requalifying because I still have one more trip this year, but I was very convinced I would come in above 50000 after this last trip. However, two segments came in below the "approximate miles" shown in my reservation.

DTW-MEM shows in reservation as approximately 621 miles, but posted as 610. LAX-DTW is 1982 in the reservation, posted at 1979. I see that the miles posted as per the mileage calculator. But I had neglected to check the mileage calculator, instead trusting the "approximate miles" displayed in the reservations system. If this had been my last trip of the year I would have gotten burned.

Does anyone know why the reservation system can't report actual mileage?

Think about this carefully. Do you really want to cross that threshold? Nobody else will ever be closer to Gold than you!

I suspect the mileage estimates are the output from some generic great circle calculator. The actual mileage credited can even vary slightly by airline.

Yes, I really do. I must prefer to be the GE with the fewest # of EQMs than the SE back in coach that was the closest to making it.

And isn't the actual mileage that posts also calculated by some generic great circle calculator? Or do they actually send out a team with a very long measuring tape to calculate the actual miles?

I think you missed the sarcasm, or simply ignored it...

I always thought they just read the odometer on the plane.

It's one thing for the mileage on a codeshare flight to be off a bit. But for NW metal flights booked on nwa.com, there's no excuse for the discrepancy.

Just curious what the excuse for the former would be that wouldn't apply to the latter...?

FWIW, as previously posted, the mileage calculator on nwa.com is the most accurate. Until all the distances align, that's your best bet from nwa at getting an accurate figure.

And as a tidbit of data, I just checked four sources for a random routing (MSP-IAH) to see what they say:

• nwa.com reservations: 1,059 miles
• continental.com reservations:1,048 miles
• nwa.com mileage calculator: 1,034 miles
• gc.kls2.com great circle mapper: 1,034 miles

So, obviously there's a little disagreement. Personally, I average the great circle mapper & the nwa.com mileage calculator. It's also important to note that the mileage listings on the nwa.com reservations pages list the distance as "approximate". Of course, all that really matters is what gets credited to their account. Anyone have that figure for MSP-IAH?

I know that the mileage to trust is the nwa.com mileage calculator, the question remains, why doesn't nwa.com reservations use it? Haven't they been able to figure this out yet?

My theory is that the reservations systems (see the continental.com quote above) all pull their data from their respective GDS (Global Distribution System, NW uses WorldSpan) and those sometimes calculate the city code distances, so MSP-HOU. Then, on top of that, the figures themselves may be -/+ a few %. I guess that's why they say the mileage is "approximate" from the nwa.com reservations.

I don't think it's a function of them "not being able to figure it out yet" as much as it is a function of their reservations systems pulling the figures from their GDS rather than calculating it from the great circle route. Plus, nwa.com reservations is powered by Orbitz, so it may be an Orbitz or other supplier issue (i.e. WorldSpan).

At least that makes some sense (with the figures not coming from nwa itself), but you'd think someone would have corrected those figures in all the GDSs, including calculating based on the airport codes instead of the city codes.

At least they do say approximate.

If that's the reason, I'd guess it's not one of the highest priorities they have. Thankfully, anyone reading this thread now knows of alternatives.

Thanks mostly to FT (lots of threads, not just this one), there are a lot of us who know that now. I know I've only really trusted the nwa.com mileage calculator figures, and they've been super accurate for all my flights compared to what posted.

Sorry, but I don't have MSP-IAH (don't often go between CO and NW in one trip, and I definitely have no plans to end up in IAH in the near future...)

Other IAH segments I have flown within the past year include:
SFO-IAH CO OP, posted to NW as 1,635
PIT-IAH CO OP, posted to NW as 1,117,
IAH-YYC CO OP, posted to NW as 1,747
IAH-TUS CO OP, posted to NW as 937

Hope that some of these datapoints help in your quest to figure out which system is reliable

I love it when the flight attendants say "WP members will earn approx ... pause ... XXXX miles" as they read it off the sheet. Clearly nobody is paying attention, or cares.

Everyone agrees to the mile with http://www.nwa.com/cgi-bin/wpmiles.cgi and on MileCalc :: The Ultimate Mileage Calculator for Frequent Flyers, the top three agree but the fourth comes up as 936 (probably the difference is an issue with how the two round off to an even mile).

Most of us that care already know.