crooked bounding box leads to crooked model

hi there
i've run into some difficulties with my new 737 model.
the fuselage appears straight in Gmax, but it's bounding box is crooked. so when i export into FS (i can export now
)the fuselage gets crooked as the game turns the bounding box straight.
take a look:

how can i reset the bounding box?
i've run into some difficulties with my new 737 model.
the fuselage appears straight in Gmax, but it's bounding box is crooked. so when i export into FS (i can export now

take a look:
how can i reset the bounding box?