See what it says on your personal stats (F8) and there a line called Level Up Requirement or similar. Odds on it's a monetery figure. You need to make more cash.

If it wasn't for the inky blackness of the night you wouldn't appreciate the brilliance of the stars...

Thanx for your reply, but in my status the requirement is "Mission"?
What does it means? What mission? Number of missions?

It means that you got hit by the 'stuck level' bug and I'll bet a virtual sixpack that you have applied the server patch to your game. Bad idea. Your best option is to reload a savegame from before your net worth exceeded the threshold for level 28 (646965 credits IIRC). Chalk the extra flying time up to experience.

It means you either haven't finished the SP campagin or there is a bug, much more likely the second one. Perhaps you accepted a mission somewhere you didn't finish yet? Other then that I don't know what could have happened. Are you using any Mods?

Live Long and Prosper.

Thanxs Mr Spock.
I'm playing without mods, for the moment, and as far as I remenber I finished all missions.
Of course sometimes I've aborted missions (twice as I remenber).
Probably it's a bug of Freelancer.
What about "spending" a lot of credits to get bellow the maximum credits level allowed for level 28?
I'll try it and I'll report the result.
Regards