The new Disney movie "The Last Flight of Noah's Ark" toys with enough ingredients to supply half a dozen adventure sagas. Unfortunately, it never takes off and sustains imaginative flight on the strength of any prototype, from Noah's Ark to the Kon-Tiki or "Robinson Crusoe" to "The African Queen." A low-octane adventure fable. "Last Flight" keeps sputtering out on the stodgy, overprotective mechanics typical of Disney juvenile entertainment.

Derived from a story by Ernest K. Gann, whose fiction brought the movies such aerial suspense stories as "The High and the Mighty" and "Fate Is the Hunter," "Last Flight" relies on an appealing pictorial centerpiece -- the use of an old B-29 as a versatile prop. When the tarnished but serviceable bomber, carrying supplies and livestock to a mission in the Pacific, is forced to crash-land on a solitary island, the survivors contrive to transform the flying machine into a sailing vessel. Serenely majestic in flight, the plane retains its dignity after being clipped of its wingspan and outfitted with mainmast and rigging.

The passengers, alas, aren't nearly as engaging or adaptable as the B-29. Maladroit Choice No. 1 is lumpy, callow Elliott Gould as the pilot, a cigar-chomping ne'er-do-well hired on short notice when he turns up at Vincent Gardenia's rundown airdrome fleeing gangster creditors. Gould is meant to play Humphrey Bogart to the Katharine Hepburn of Genevieve Bujold, a dedicated, spinsterish missionary bound for a remote post. If the chemistry had worked, "Last Flight" might have evolved into an airborne and seafaring variation on "The African Queen."

The ill-chosen romantic leads are further encumbered with juvenile competition in the form of two stowaways -- Ricky Schroder (the overdemonstrative discovery from "The Champ") and Tammy Lauren, who are loath to part with beloved animals, a water buffalo and a duck, respectively. Although the youngsters' backgrounds never ceased to perplex me, I gather that Schroder and Lauren may be orphan wards of the same agricultural missionary organization that supposedly sponsors Bujold. At any rate, it confuses exposition needlessly to assemble an impromptu nuclear family out of unrelated characters: makeshift parents and makeshift siblings, none of whom seems intimately connected with the others.

A preferable set of adoptive parents materializes after the plane is forced down. The castaways discover earlier castaways: Yuki Shimoda and John Fujioka as Japanese soldiers still manning an island fortress 35 years after the end of World War II. Following a brief suspicious skirmish, the Japanese prove to be cheerful company and indispensable suppliers, shipbuilders and sailors.

In fact, Gould begins to look superfluous as well as seedy. When he doesn't have the courtesy to wait for the Japanese on sailing day -- they must swim out to the departing bomber, now modified into a ponderous raft -- one feels more than slightly miffed. Since the rebuilding would have been impossible without these men, it's unthinkable to launch the ship without them. i

There are several indications that the screenwriters ceased to think straight at this point in the narrative. The process of turning the beached bomber into a sailboat reawakens one's slumbering interest but it's soon nodding off again as the livestock allegedly are ferried below deck, lest the kiddies miss their pets and Ricky Schroder throw a crying fit. This would seem the appropriate moment for some realistic sorrow, with sad but inevitable partings between little humans and the animals they must leave behind.

On the contrary, the whole flock seems to come aboard again. Of course, if the film bothered to depict the labor actually necessary to reload chickens, pigs, ducks and water buffaloes and then care for them during a sea voyage of unknown duration, even the kids in the audience (whose tender feelings are supposedly being protected against cruel necessity) might wonder why a little sacrificing wasn't done.

I'm not sure how seaworthy the old bomber would be after the conversion depicted in "Last Flight." It doesn't appear to be making much headway over the waves, a consideration that puts a heavier burden on that cargo of livestock, especially the water buffaloes. Nevertheless, the sight of the revamped plane floating about is strange and beguiling; a pedestrian movie is graced with fleeting charm and distinction. It's not every film that offers a fanciful journey on such a picturesquely improbable vessel.