The Airlock Climax (Alien) Alien (1979)

Protagonist	Ellen Ripley
Mission	Kill the alien herself, with no system to lean on
Runtime	117m
Climax	beat 35b · 110m · 94% into film
Wind-down	beats 36–37 · 111m–117m · 7m long
Resolution type	validation

The climax

Ripley believes the alien died with the Nostromo and discovers, in the shuttle's wall, that it stowed aboard the Narcissus.^{b32 b33} She suits up one motion at a time without waking the creature,^b34 then straps into the pilot seat, arms the harpoon gun, sings "You Are My Lucky Star" to control her breathing, opens the hatch, and harpoons the alien — which the decompression drives toward the door but which clings to the shuttle's exterior by the line.^b35a

The audience-certainty moment is the engine blast.^b35b Ripley fires the shuttle engines; the exhaust blows the alien off the hull and into deep space; it tumbles away into the void. Until that moment the alien is still attached to the Narcissus — the harpoon hit has not resolved the threat, only positioned it. The engine firing is the gesture that converts the position into a verdict. The shuttle is clean.

The wind-down differs because

Ripley's final log and the move to hypersleep with Jones close the new equilibrium rather than test it. She names every dead crewmate, dates the report, signs off as "last survivor of the Nostromo,"^b36 and gets into the pod with the cat.^b37 The mission's outcome — total self-reliance survives — was settled the instant the alien tumbled away. The log is the executed paperwork of the new reality, not a further test; the address-to-no-superior is the new equilibrium image.

Why this is a validation climax

The post-midpoint approach forms across the back half. Ripley queries Mother directly (Midpoint, b23) and finds Special Order 937. Ash attacks her; Parker takes his head off (b24). She announces the self-destruct without a vote (b26), activates it alone (b29), incinerates the cocooned Dallas instead of attempting rescue (b30), screams at Mother when the override expires (b31). By the time the alien is revealed on the shuttle, the new approach — abandon the system, act on her own judgment — is fully built. The airlock climax tests that already-formed understanding under maximum pressure: no Dallas to give the order, no Ash to consult, no Mother to query, no Company to obey. The procedure she runs at b35a–b35b is hers. The engine blast is the test holding.