Because Malta enters the EU in 2005(May, IIRC). Then you can.
In the meantime, you can either stockpile owned planes for a quickstart in 2005 elsewhere, or play the plane broker game.
EDIT : or replace your leased planes by owned planes, to improve your margin. If some of your leases come to an end soon, it would be a wise use of your cash. Or prepare a fleet replacement, MD80 will get outdated sooner or later, and you won't keep them until the end of the game(you are not in a hurry either). You have plenty of possible directions to improve your company before 2005.