Half a decade after terrorist attacks climaxed in the Mediterranean basin, three involving airliners, security at the much-maligned Athens airport has been substantially upgraded.

That's according to the officials in charge of security at the airport. And a walk through security checkpoints in late May showed that equipment and personnel have been added and the training of staff upgraded.

But people who use Hellinikon International Airport frequently still are not satisfied.

Greek travel agent Nikos Tziotis, owner of Athens-based Mycenae Travel, calls security measures now "medium ... about as good as it can get at an airport" without unduly interfering with customer service. But Marios Angelis, owner of Aerotours of Athens, goes farther. "There is a general feeling that security is bad. It's just show-off, just to scare the amateurs, like the guards who stand in the banks with machine guns."

A total of 13.6 million foreign passengers passed through Greek airports in 1989, 6.2 million of them through the Athens airport, which -- along with the rest of the Mediterranean basin -- has been considered a nexus of international terrorist activity since the mid-1980s. In 1985, the hijacking of a TWA flight out of Athens left one American dead; the hijacking of the Achille Lauro cruise ship in the Mediterranean Sea left another American dead; the hijacking of an Egyptair flight out of Athens resulted in 60 people being killed; and two machine-gun massacres -- one at the Rome airport and one at the Vienna airport -- left 19 people dead. In 1986, the mid-air bombing of TWA flight 840 as it approached Athens resulted in the deaths of four Americans.

Today, most of the electronic screening equipment at the Athens airport has been renewed, including the addition of new X-ray equipment; the periphery fence, once riddled with gaping holes, has been reconstructed at damaged and high-risk points; and the security staff has been doubled to more than 1,000, including special bomb-detection squads with dogs and electronic sniffers, 24-hour patrols and special anti-terrorism "green beret" units, according to Lazos Vafias, head of security for the Greek Civil Aviation Authority.

Now when you enter and leave the terminal through the electronic front doors, you see a shiny blue armored car with a menacing turret, and one policeman and a "green beret" guard the doors with sub-machine guns. Police inside conduct spot-checks on "suspicious" characters, opening their luggage for a thorough search. Cameras survey every corner of the departure and arrival halls. No luggage is allowed on an airplane without being matched with a passenger.

Passengers pass through an electronic security check, an X-ray machine and metal doors at the main airport checkpoint. Transit passengers, about half a million annually, pass through a separate electronic checkpoint. Employees who move from one part of the airport to another also must pass through a metal door. And some airlines provide their own security clearance areas at the gates.

On the airport periphery, there are other security measures in force, with only authorized airport and customs vehicles allowed on the tarmac. But on a recent drive I took around it with security officials, they could not immediately identify some vehicles. And a bar across one security gate, the second of two we had to pass through, was up in the air with no attempt by the guard in the booth to ascertain who was passing.

Travel agent Tziotis says the current safety measures aren't enough, and cites a recent experience with a demanding American businessman at the airport. For 10 minutes the businessman stood in front of the airline counter being questioned by the check-in clerk.

"Is this your suitcase?"

"Yes."

"Did you bring it from your house?"

"Yes."

"Did you pack it yourself?"

"Yes."

"So you know what's inside?"

"Yes."

"Thank you and have a pleasant trip."

All the while the man stood first on one leg, then another, murmuring his answers, worrying about the other 200 passengers who still had to go through this process and about missing his flight. After complaining under his breath continually to Tziotis, he came out of the little interview unimpressed: "They let me go too easily," he said and stalked off to catch his flight to New York.