Israel's successful response to the flight will be predicated on a clear understanding of objectives. Is the mission to enforce the aerial blockade no matter the cost? Or is it to do so without harming the passengers aboard the aircraft? Hopefully in the wake of the Mavi Marmara raid, Israel will chose the latter. Although conceivably there will be less video footage of a plane being shot down at 4000 feet than a boat full of journalists. Unless there are journalists aboard the plane. In which case Israel is killing not only civilians but journalists. As you can see, the levels of complexity quickly multiply. Irregardless, Israel has essentially five options for dealing with this situation:
Option 1: Shoot down the plane. 100% enforcement of the blockade, but the PR costs will far outweigh the benefits. Acvitists will build on the anger from the Mavi Marmara to build pressure on Israel to relax the blockade even more. The activists win, Israel wins the battle but loses the war. Bad choice.
Option 2: Shoot to disable but not destroy the plane, forcing an emergency landing. This option is extremely dangerous and runs the risk that a strike intended to damage the plane may lead to the deaths of the passengers anyway. Because footage will survive, it still allows for negative PR against Israel. Activists probably win, Israel probably loses. Dangerous choice.
Option 3: Escort the plane to the ground and arrest the activists. This raises the question of where to escort the plane, and what to do if the plane refuses to comply (a pretty safe assumption). Conceivably the Israeli Air Force might be able to force the plane to stay airborne enough for it to run out of fuel and force an emergency landing, but the details of this option are better known to aviation experts. Israel might maybe win assuming the plane can be forced to land, but it would take a more detailed understanding to realistically assess the validity of this option. Unclear choice to a non-expert, perhaps clear to an expert.
[UPDATE: According to someone who knows much more about the technical aspects of these options, a plane cannot be targeted with the intent of non-catastrophic damage. However, it can be forced to land given the pilot does not ditch the plane intentionally.]
Given the unsavory nature of all of these options, the most likely course of action will be:
Option 4: Use diplomatic pressure to prevent the flight. An ounce of prevention is worth a pound of cure, and especially in this case. Israel (and the United States, who has an interest in preserving Israel's interest in peace talks) can use diplomatic pressure to prevent the activists from filing a flight plan to Gaza from the country of origin. Of course, this kind of pressure relies on the kinds of good relations which Israel is hard pressed to find in light of its government's current isolationist stance.
Given the current situation, the ideal option would be:
Option 5: Invite the activists, on international satellite networks, to be part of a "special humanitarian observer" delegation to Gaza, in which Israel delivers the aid via Israeli aircraft. Stress that the flights are part of a routine humanitarian program to the Gaza strip and cast Israel as caring more about humanitarianism than the petty enforcement of a blockade. Israel should seek to "own" the human rights turf as much as possible by using the language of human rights in its PR rhetoric. Activists should be cast as radicals who care more about political turf than helping actual Palestinian people. This option won't win over the far left activist base, but it will mitigate damage done to Israel's image in the minds of centrists. Oh and also it serves the needs of the Palestinian people, who I hear need a little help.
Of course, the bigger issue Israel will have to deal with is the validity of an aerial blockade in the first place. In the sense that Israel wouldn't want foreign cargo from enemy states (ie Iran) landing in Gaza, this blockade is pretty reasonable. However, it will take pragmatism on the Israeli side to justify its policies. The global public is much more likely to accept a blockade on illegitimate items if legitimate items are allowed through. Banning chocolate for Gazans is not really an effective means of creating this public acceptance. And the bigger picture here is that PR and military strategy for Israel are not two separate arenas, but one and the same. This situation is a perfect example for Israel to show the world that it understands the connection between the two by pursuing a nuanced, responsible course of action which meets the needs of its citizens while respecting the needs of the Palestinian people as much as possible.