In a situation like the current Tel Aviv one it will be the insurance market that will be calling the shots. The insurers can do a number of things, the two most likely are to 1). Suspend all insurance for aircraft flying into Tel Aviv, or, (and more likely in this case), 2). Charge an additional premium for each and every flight. It may be worth the extra for some airlines and not for others. Airlines that lease their aircraft may have to comply with the instructions of the leasing company too.