The 23-year-old flight attendant had been suspicious of the slim passenger from the moment he boarded the National Airlines Convair CV-440 in Miami.
"He had dark glasses on, his collar up, unshaven, right out of Mickey Spillane," Harlow, now Inez McDermott, said in a recent interview. "He was abrupt and rude."
When she turned around after spending a few minutes in the galley and didn't see the strange man, she marched toward the unlocked cockpit and went through the curtain.
"I saw him with a gun on the copilot, who looked pea green, and he had his arm around the neck of the captain, with a knife," she said. "My knees went weak."
The first aerial hijacking of a U.S. passenger plane had begun.
The crew and the handful of passengers survived the ordeal, in which Puerto Rican-born Antulio Ramirez Ortiz forced the captain to divert the Key West, Fla.,-bound flight to Havana. It was all over in a day.
But for the American people, flying would never be the same.
Fifty years later, U.S. air passengers face a phalanx of background checks, body scanners, metal and explosives detectors and an exacting list of more than 70 prohibited carry-on items, including snow globes and certain types of screwdrivers. They arrive hours early for flights to run the security gantlet and navigate check-in.
At airport checkpoints, they wriggle out of shoes, coats and belts, extract from their carry-ons quart-sized bags of 3-ounce (and not more than that) containers of liquids and gels. They slap portable computers onto conveyor belts, and they hope they don't get pulled aside for enhanced pat-downs by security officers.
Travelers can be forgiven for asking these two key questions: Is it worth it? And how did we get to this point?
On the first question, doubters abound. But many security insiders answer "yes," with this caveat: Air travel will never be risk-free.
As for the second question: The fight to secure U.S. aviation has been a halting, painful journey, replete with tragedies and heated debates that have tested our nation's values. And we're nowhere near the end.
We are, however, at a crossroads, said terrorism expert Brian Michael Jenkins, senior advisor to the president of Rand Corp., the Santa Monica-based think tank.
As privacy guardians squirm and critics liken pat-downs to groping and full-body scans to virtual strip searches, "we are beginning to approach the edge of passenger tolerance," Jenkins said.
With air traffic on the rebound, forcing more people to squeeze through checkpoints, the system may soon stagger under its own weight. Many experts are calling for a new approach to screening.
In 1958, when McDermott signed on with National, airline security wasn't a big issue. In fact, it was nearly nonexistent.
Although the cockpit door on the hijacked plane had a combination lock, captains often left it open and just drew a curtain, she said.
Back then, boarding a domestic flight was a breeze. Even international passengers might arrive only an hour ahead. There were no metal detectors or screening checkpoints. "Carry-on" meant a hat or coat, tossed onto open shelves in the cabin, or whatever fit under the seat.