The movie business is suffering one of its recurrent sickly spells. A season in which "Hopscotch," "Private Benjamin" and "It's My Turn" loom as box-office favorites cannot be regarded as profoundly gratifying. Glum exhibitors don't expect much relief from the Christmas offerings either.

The scarcity of potent first-run attractions came home with a vengeance last weekend, when five far-flung obscurities opened here: "The Apple," "Arabian Nights," "Lovers and Liars," "Hangar 18" and the "Kidnapping of the President." It might have been better to throw together random footage from all five and release it as a novelty compilation called "They Came From Out of the Woodwork."

"Hangar 18" and "The Kidnapping of the President," doltish thrillers aimed at lowbrow conspiracy freaks, can be lumped together and deposited on the same junkheap.

"Hangar 18" is the sort of UFO cheapie that "Close Encounters of the Third Kind" should have made obsolete. On the contrary, "Hangar 18" carries on in the pseudo-revelatory tone of earlier visionary balderdash (make way for the chariots of the gods!) while trying to string out a suspense plot that relies heavily on situations cribbed from "Close Encounters" and "Capricorn One."

The action begins with a comic collision in outer space. The crew of an American space shuttle launches a satellite which immediately crashes into a hovering UFO. This disaster permits the filmmakers to display a shocking effect with their laughable special-effects budget: One of the astronauts has been tethered outside the shuttle and gets head severed by passing debris; still inside his helmet, the severed head rotates into the void along with the rest of his body.

The filmmakers seem to be similarly afflicted. The space crash drops a UFO into the Arizona sagebrush. The military gets the vehicle into a secret lunar receiving laboratory, Hangar 18, located on an air base in Texas. This in itself would be an epic feat, but it happens off-screen in the dead of night.

While NASA official Darren McGavin and a team of scientists proceed to explore the alien craft -- a squat three-tiered pyramid that resembles a plastic toy -- the surviving astronauts (Gary Collins and James Hampton) return from their flight. They discover a Cover-Up and set out to find the truth, which naturally causes them to get into chases and fights with FBI agents and to become desperate outlaws.

The party responsible for this pointless conflict is a presidential assistant played by Robert Vaughn. The president is in a tight reace for re-election; having ridiculed his opponent for professing a belief in UFOs, the president cannot afford to acknowledge their existence. Hence, Vaughn is determined to keep the lid on through Election Day. Vaughn ultimately decides to cut his losses by authorizing a mission to blow up Hangar 18. Presumably, no one will be the wiser.

And what about the UFO? Well, it might be boon or bane; the filmmakers decline to clarify their speculation. After breaking a language code and studying the records on board, McGavin's team seems ready to conclude that the Missing Link has been identified.It appears that a master race of aliens descended in prehistoric times to impregnate our primitive females. On the other hand, the aliens have also been studying all our power and defense installations. Missing link or not, these godlike visitors may be up to unsavory monkey business.

Vaughn's scheming aide should go into disaster-prone partnership with the bumbling Secret Service agent played by William Shatner in "The Kidnapping of the President." In his zeal to protect the chief, a crusty-folksy type played by Hal Holbrook, during a visit to Toronto, Shatner contrives to make it easier for the president to be handcuffed in a crowd by a daring terrorist wired with TNT and then imprisoned inside an armored truck also designed to explode at the faintest touch.

A gruesome prologue establishes the bloodthirsty resolve of the terrorist mastermind, Robert Assanti, played with considerable nasty authority by Miguel Fernandes. Assanti directs the killings of several members of his guerrilla band, completing the executions by slitting the throat of his own girlfriend, a radicalized American coed.

Receiving a tip that this fiend is headed for Toronto, Shatner urges extra precautions but is stymied by contradiction from the CIA and the president's desire to be chummy with crowds. The kidnapping scheme is revealed to be a cumbersome affair that ought to backfire on several occasions. For example, the armored truck overheats, so the kidnappers start their day by shooting it out with police at a gas station and then blowing up the station in order to make a clean getaway. (Could these people possibly be acting under instructions of Robert Vaughn from "Hangar 18?")

Once in the vicinity of the president and Canadian prime minister, the armored car is allowed to slip through barricades and overwhelm suspicious security people. Assanti's principal confederate, the deceived sister of his late girlfriend, slips out of the truck in plain sight and eludes hordes of armed guards. After all, someone hs to remain a threat to detonate the truck after Assanti starts negotiating ransom terms ($100 million in diamonds) with the authorities.

As soon as he's snatched, Holbrook orders Shatner to knock off the kidnapper, dynamite or no dynamite. Although 3 or 4 dozen sharpshooters have the culprit's head in their sights, Shatner is obliged to cool it, lest the movie end prematurely. He hesitates until Holbrook is locked inside the armored vehicle and commences to dicker with the smug, contemptuous Assanti, getting even by calling him rotten names each time he's out-smarted.

Although it appears that Shatner's character should never have gotten out of bed, he's allowed to take charge of the rescue operation -- at the express order of the prime minister. (Can the PM be in league with the terrorists and Robert Vaughn?)

While the president broods inside the boobytrapped vehicle, emergency powers devolve on Vice President Van Johnson, a weakling who has just admitted taking a $25,000 bribe. "I put it all in the bank!" he wails in self-defense, but Holbrook says he has to resign anyway. Although Johnson does nothing to distinguish himself during the crisis except stand up to his power-hungry wife, Ava Gardner, he is curiously forgiven his trespasses at the fadeout. One gathers that the $25,000 will never be mentioned again, at least in the Oval Office.

From a strictly technical stand-point, "Kidnapping" is a far more professional and presentable stinker than "Hangar 18" -- which is nothing to tackle in a drowsy mood. But maybe that's the idea: While director James Conway puts customers asleep, aliens silently steal into the auditorium and have their way with the womenfolk.