I have zero problem with the basic premise and here's why.
The bioterror angle Zarb explored is easy, but just to think out loud for a second … what if not? Organs for transplant are carried on commercial flights all the time, as carry-on packages in the passenger cabin.
We open on a narrow, winding road somewhere in the tropics. It's sunset, magic hour. From an aerial shot of rolling jungle-covered hills, we zoom in to a helmeted motorcyclist — obviously a woman, from her skin-tight leathers — tearing down the otherwise empty road.
Suddenly holy shit! There's a water buffalo in the road or something! She lays the bike down, skids a hundred feet down the road head-first into a tree. Smash-cut to black.
We fade in to the rider's POV. It's after dark now, but headlights light the scene with a cold glare. We see what are obviously paramedics working over her, chattering away in unsubtitled local yabber-yabber language. We see them put a mask over her nose, and inject things into her body, but the shot begins to iris out. We cut to a close-up of her face as her eyes go dead.
Next we're in a hospital. She's being rushed through corridors into an operating room. It all looks very normal, but the foreignness of it makes it somehow sinister. We're not sure what's going on; are they trying to save her, or is it something darker? She gets rushed into the OR, they cut the rest of the clothes off of her, then we get a gore-discretion montage of incisions and retractions and dissections, and then wet, dark, not-quite-seen things being dropped into stainless steel basins.
Then we do a continuity cut to a tight close-up on a small styrofoam cooler, about the size of a lunchbox, otherwise nondescript but for the big red official-looking label on it: HUMAN ORGAN. It's being carried through airport security by a young, scruffy-looking guy. He's our protagonist. Think somebody in the Bradley Cooper vein; improbably handsome, but just dorky enough to be plausible.
We're in an international airport, someplace exotic but civilized. Ho Chi Minh City, maybe. We see our guy make his way through security with like zero grasp of the local language, probably all MOS cause we're rolling the opening titles. He finds his way to his gate just as they're closing the door, and flops down in a window seat on the upper deck of the 747, in business class.
There he has a meet-cute with a Vietnamese girl next to him. She's barely legal, maybe 19. Rich parents, sending her to New York to go to school. Her English is terrible, but they flirt and laugh a lot. Because she can't read well, she doesn't realize what's in our guy's cooler. When she asks him, he awkwardly spins it around to hide the label against the bulkhead and changes the subject.
They take off, order drinks — he knows he shouldn't, but it's a long flight, and it's just a beer — and talk. She's gorgeous, and exotic, and clearly into him. We see an obvious mile-high-club opportunity in his future.
It's about this time that we hear an ominous creaking, groaning sound. For serious. It sounds like the Titanic's about to break up. The captain comes on the intercom, delivering a long speech in Vietnamese. The girl tries to translate for him. "Turbulence," she says, finally spitting out the word, grinning 'cause she got it. "That's it? That's all he said? He talked for like three minutes, and you give me one word?" They're laughing about it, but our guy is visibly anxious.
Then the captain starts repeating his little speech, this time in surprisingly unaccented English. (Commercial pilots speak English to air-traffic control; they're good at it, regardless of their native tongue.) But just as he gets to the part about rough air, the window by our guy's seat suddenly, and with absolutely no warning, explodes inward, the seal around the plexi failing catastrophically. It comes inside with the energy of a bomb, practically vaporizing our guy, his new girlfriend and, most importantly, the styro container with the transplant organ in it. That's right, folks, this is Psycho and they're both Janet Leigh.
The bulky business-class seats contain the force of the rupture for the most part, but our until-now presumed protagonists (and our mystery organ) are basically aerosolized, spraying the other passengers in the compartment with a thin mist of blood and tissue. (It'll be tricky to do this graphically enough to get the point across but not so bad we nauseate the audience.) Alarms are going off, oxygen masks are dropping from the overhead, people are start screaming once the second and a half of shock wears off, it's chaos.
But all things considered, it's not a catastrophe. Yeah, two people are dead and an international flight high over the Pacific is in danger, but it's not unprecedented. There are protocols for this kind of thing. All they have to do is declare an emergency, descend to under 10,000 feet so nobody suffocates in the unpressurized cabin, turn around and fly low and slow to the nearest airport. It'll take hours — low and slow, remember — but everybody's gonna be fine.
Until people in the upper-deck business-class cabin start getting sick.
(The contagion is definite blood-borne, and might be airborne through aerosolized mucus and saliva via sneezing and coughing. It's not spraying virus particles out the window as the plane circles, because Viruses Do Not Work That Way, but the way it spreads through the plane makes it clear that it'd be very difficult to reliably contain on the ground in a country with no real disease-control infrastructure like Vietnam. So the choices are let it land and let those guys take their chances, possibly causing a pandemic; get global ATC to divert the plane out over the ocean outside ground-based radar coverage and then covertly shoot it down; or redirect it to the United States where at least CDC containment guys have a chance of keeping the infected people secure, and just maybe curing some or all of them.)
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