Well, there are two possibilities here. The first is that they do earn profit. If so, your suggestion was entirely useless - in fact, more than useless, harmful. The second is that they don't earn a profit. This has two sub-possibilities - either they can never earn a profit, or they can earn a profit but do not currently. If the first is true, then no foreign company will buy them (obviously), and they are being run for some reason of public benefit - i.e., planes to Rhodos, which is heavily isolated from basically everywhere and requires an airport just to receive basic goods and so on. Selling these does not help. If the second is true, then, yes, I suppose you could sell them to a foreign company and it would act as a short-term gain - but the emphasis is on short-term, because you then get a one-time piece of sales revenue, almost certainly at below market value given the nature of the sale, whereas if you took the time to improve these assets yourself, you go back to the very first possibility, in which they earn profit that the Greek government benefits from.
So, remind me again, why are we arguing for privatizations in the context of a government with income problems?