Ask any hapless traveler in this land to name communism's greatest enemy and the list might include not only occidential imperialists or oriental hegemonists but also the comrades who run Soviet trains and planes.

Rail transport is a kind of chaos that would try the patience of any Amtrak veteran. It is not simply a question anymore of trains failing to run on time. They go to the wrong places and lose their cargoes enroute. In some cases, they have disappeared.

Even the chief engineer, President Leonid Brezhnev, is short-tempered over the railroad's performance. He blamed rail bottlenecks and laggard ways as chief contributors to the Soviet Union's woeful economic report for 1979, when the gross national product expanded by the smallest percentage since World War II. The Soviet press recently offered a prime example of the kind of problem the leader is complaining about.

This tale begins in Moldavia, a small republic lying between the Romanian border and the southern Ukraine. In an effort at regional cooperation and improved efficiency, authorities in the two areas divided responsibility for the main line, about 120 miles of track, connecting the important Ukrainian Black Sea port of Odessa and Kishinyov, the Moldavian capital. On the inaugural day of the new system, a freight train headed southeast from Moldavia, crossed into the new, separate Odessa control zone -- and disappeared.

Worse than never reaching its destination, it never returned to Kishinyov. There, the Moldavians had just completed a big fruit and vegetable harvest and needed all their locomotives to ship their cash crops north and east to Siberia and the Far East before the produce rotted at the depot.

In a barrage of telephone calls, telegrams and letters, the Moldavians sent out the alarm for their missing train. Meanwhile, they dispatched another train for a round-trip haul to Odessa. It also vanished.

The Moldavians, now desperate for engines, urgently appealed to a locomotive factory for help and the factory quickly sent three of its newest models. Locomotives ZTE 0001, 002 and 0003, headed for Kishinyov. Unfortunately, the track from the factory to the capital took them into the mysterious Odessa control zone. They never emerged.

"I don't know anything about this," declared the head of the Odessa rail region. "I'll certainly look into it." He didn't.

While he sat on his hands, tales took shape in Kishinyov of Odessa rail workers commandeering Moldavian engines and putting them secretly to work in their own freight yards so they could fulfill their economic plan and win big bonuses.

Moldavia appealed to the national Ministry of Transport in Moscow, which rapidly ordered the three new locomotives to be returned to Kishinyov "within 24 hours [or] this matter will be referred to the highest authorities for a full investigation."

Days later the Moldavians won release of engine number 003, but the others did not turn up. The Odessans apparently had hidden them on branch lines to pursue their economic goals before the locomotives were discovered. The Communist Party newspaper Pravda, which recently revealed the Odessa piracy, asked plaintively: "How is it possible that the Ministry of Transport is unable to enforce its decrees, even those delivered with thunderous threats?"

The railway authorities in their difficulties may take some comfort from the problems of their more glamorous sister service, Aeroflot. The national airline enjoys describing itself as the world's largest, which it is.

Last year, Aeroflot hauled more than 100 million passengers around the Soviet Union and made connections to more than 80 foreign countries. Its pilots routinely fly into some of the smallest and most remote airports on earth. They also dust crops, haul gas pipeline, ferry oil prospectors, and carry gold and diamonds from isolated mining camps under special guard to government repositories.

For an airline, it seems to do just about everything. Except make its schedules.

This year, for reasons that may relate to possible fuel shortages but have so far gone unexplained in the official press, the delays seem worse than ever. s

The recent experience of one member of the American press corps here, NBC correspondent Gene Pell, gives some of the flavor of the problem. On Thanksgiving, Pell headed for Tbilisi, the capital of Soviet Georgia, on a story. He arrived at Domodedovo Airport on the edge of Moscow in good time for his 8 a.m. departure to discover that flights from the day before were just being scheduled.

He settled in for an all-day wait. About midnight, he and other Tbilisi bound foreign passengers were bundled into a bus to take them to the plane. The vehicle wandered around the darkened field for 20 minutes as driver and Intourist attendant searched for the right aircraft. They found it on the fifth try and the passengers lined up to board.

No stairs. After long minutes in the frigid darkness, the stairs arrived. The attendant climbed up to open the door. It was locked and she had no key. More waiting while Aeroflot searched for the key. Finally, the door was opened and the passengers crowded forward once more. But there was no crew. At that point, Pell gathered his bags and headed back to Moscow, reaching home 24 hours after he departed.

Had he taken the train, he would have just about been arriving in Tbilisi -- providing, of course, the train hadn't disappeared.