Northwest Airlines Flight 714, bound from Tampa to Miami, was barely ten minutes off the ground when a slightly built man in a baseball cap, brandishing a hunting knife, wrestled a stewardess into the seat next to him and demanded that the plane go to Cuba. The captain of the Boeing 727 dutifully changed course. Across the aisle, Miami Cargo Shipper Dewey Parker silently signaled to Blake Bell, the passenger in the window seat next to the hostage stewardess. "On the count of three, he grabbed the hijacker's right arm and I grabbed his left," recounted Parker, "and then we got assistance." Tied up in seat belts and an oxygen mask cord, the would-be sky pirate, a former political prisoner in Cuba named Rodolfo Bueno Cruz, was arrested upon arrival in Miami. "I don't criticize it," said FBI Agent Jim Freeman of the risky rescue, "but I don't recommend it for everyone."

The foiled attempt came one day after the Federal Aviation Administration (FAA) announced an intensified campaign to combat a rash of southbound skyjackings. Since May 1 eight planes have been hijacked to Cuba, including two last week. Among the new steps: more thorough and frequent baggage checks, the installation of 14 "state of the art" X-ray machines at Miami International Airport, and a beefed-up force of FAA inspectors at other South Florida airports.

Potentially more effective are FAAsponsored public service announcements, broadcast in Spanish and English, that will warn Cubans of the long prison terms they face in their homeland for high-altitude high jinks. "We are trying to tell them if they want to get back to see Mommy and Daddy, the only time they'll be able to see them is on visiting days," said FAA Spokesman Jack Barker. Indeed, Cuba is uncompromisingly harsh on its airborne returnees, handing out sentences of up to 20 years for air piracy. "There are no air-conditioned cells with televisions in Cuban-jails," said Jim Ewing, spokesman for Delta Air Lines, one of the hijacked carriers. "They're tough."

The warnings may fall on deaf ears, regardless. Most of the eight recent hijackings were carried out by homesick refugees, part of the wave of 125,000 Cuban exiles who washed up on South Florida's shores during the 1980 Mariel boatlift. Disillusioned with their new life in the U.S., they discount talk of prison terms as American propaganda. At present, Havana refuses to do the one thing State Department officials believe would deter potential sky bandits: extradite them back to the U.S. for prosecution. Cuba has done so only once, in 1980, and the two returned hijackers were sentenced to 40 years apiece in federal prison.

U.S. airline representatives applauded the FAA's redoubled efforts, but were skeptical that the pirates could ever be foiled entirely. "If they say they can stop hijackings," said Delta's Ewing, "let's hope they can. We're taking a wait-and-see attitude." Indeed, a preboarding body search and stroll through a metal detector failed to reveal Hijacker Cruz's knife. Said Jim Ashlock, spokesman for Eastern Air Lines, whose jets have been involved in three of the last eight Havana landings: "If we had better techniques for preventing hijackings, we'd be using them."