spaceship- or aircraft-style camera

Example: The camera is looking into the direction of the negative z-axis. The it pitches 90 degrees up (so you look straight up). Next, the camera rotates around the z-axis with 90 degrees.
In other words, it is like you are sitting in an airplane with an pitch of 90 degrees and looking left or right over your shoulder).
Using the simple syntax (rotation around the x-axis and then around the y-axis with glRotate*)
has the result, that the imaginary horizon (the x-z-plane as a surface) ‘cuts’ the screen into a upper and a lower half - and not as it has to be in a left and a right half…
Can anybody give me a small hint to solve this problem?