Here is info on what an EQS is from http://www.nwa.com/worldperks/elite/overview.html

Elite Qualifying Segments
Members who don't necessarily travel far in mileage but fly frequently can qualify for Elite status based on the number of segments flown. All paid fare classes eligible to earn WorldPerks miles on Northwest or any of our Elite Qualifying Airline Partners will count towards your Elite Qualifying Segments (EQS) for the 2007 program year (Continental Airlines flights in Q, I, S, W, T, X, L classes; Delta Air Lines operated flights are excluded).

The following partner inventory classes will qualify for Elite qualifying segments:

Airline Fare Class
Northwest P, F, J, C, Z, Y, B, M, H, Q, V, L, T, K
KLM P, F, J, C, Z, S, B, M, H, Q, V, L, T, K
Air France P, F, J, C, D, I, Z, Y, S, G, A, B, M, K, H, T, R, L, N, V, Q, U, W, E
Continental Airlines J, C, Z, A, D, Y, H, K, N, B, V, U
Aeromexico Y, B, J, A, D M, S, K, Q, N, H, X, T, L, V
Alitalia J, C, D, I, Y, B, M, H, K, V, T, N, L, O, Q, X, W, A
CSA Czech Airlines C, D, Y, M, B, H, T, L, Q, V, I, S, G, U, W
Korean Air P, F, Y, M, J, C, K, T, H, Z, L, X, O, V, S, W, E, R
Air Europa C, D, Y, M, Q, V, K, W, X, B
Alaska Airlines F, Y, B, M, H, Q, V, L, T, K, G, S, U
Big Sky Airlines P, F, J, C, Z, Y, B, M, H, Q, V, L, T, K
China Southern F, A, C, D, Y, W, T, K, H
Copa Airlines J, C, Z, Y, A, D, H, B, Q, V, L, T, K, F, S, Z
Gulfstream International Airlines J, C, Z, Y, A, D, H, K, N, B, V, U
Hawaiian Airlines P, F, J, C, Y, V, Q, B, S, X
Malev Hungarian Airlines C, Y, D, M, B, Q, L, T, K, B, G, X