Is the act of management, by showing courtesy to some parties at the airport, considered an implicit approval of them? Is it permissible to benefit from special passenger invitations that are deducted from the profits of a public sector company? And how does this compare to zakat?

If the management responsible for the workers permits eating meals, then there is no objection to it, whether the permission is verbal or customary, or indicated by circumstances and evidence. For what is known customarily is like what is stipulated conditionally. The issue of zakat (definition) and those who work on it has no relation to the consumption of these meals.