The head of the air traffic controllers union warned three "noncooperating" airlines yesterday that they might trigger nationwide air traffic slowdowns unless they allow controllers to make free, inconditional "familiariazation" flights to Europe and the Far East.

John Leyden, of the influential Professional Air Traffic Controllers Organization (PATCO) said several of the nation's 15 domestic carriers have angered the controllers by refusing frequently a let then ride free in cockpits as observers of overseas inflight techniques.

THose flights are part of a contract PATCO has with teh Federal Aviation Administration. FAA employs the 17,000 controllers (most of the PATCO members), who handle the nation's military and civilian air traffic control lanes.

The airlines themselves are not parties to the FAA-PATCO contrsct, but most os them allow controllers to ride free in cockpits, making up to eight domestic and one international flight a year.

An aviation industry spokemen who asked not to be identified pointed out that airlines like to remain on good terms with the controllers. "Time in the sir," he said, "costs a lot of money."

A similar squabble between PATCO and the airlines over free flight space was settled in 1975, Leyden said, after a six-day "job action" that slowed airport arrivals and departures in many cities.

Three airlines, Pan American, Trans World Airways and Northwest Orient (now grounded by a pillots' strike) have refused to let the controllers make unconditional free flights, sometimes bumping them fro extra crew riders.

Leyden said the flights are beneficial to controllers, the airlines and the public. An FAA spokeman agreed that the flights are a "valuable training tool," but added that they are "subject to the approval of the airlines."

At a press conference yesterday, Leyden said PATCO members are "fed up" with the lack of cooperation by the three airlines over the free flights. He predicted a "spontaneous" slowdown, caused by members working by the book, could hit "today, tomorrow or anytime."

leyden said the union hjad just completed its Las Vegas convection where delegates mandated PATCO to push fro the overseas flights. He said the militant organization has a "national defense fund" to take care of members who run afoul of FAA for alleged work violations.

Air traffic controllers are better paid and trained and have jobs that are more nerve-racking tha the average civil servant. Leyden said because of their unique skills and position, controllers "don't have to sit back and take their lumps as most feds do."

Strikes against the government are illegal. Penalties range from dismissal to a stiff fine and / or a year and a day in jail. But as a practical matter, federal officials say they are hard pressed to stop skilled employes like controllers from working by the FAA rulebook, using separation and handling techniques that have, in the past, caused massive slowdowns.

The aviation industry depends on split-second timing to move passengers and cargo quickly and safely. Leyden pointed out that one airport, Chicago's busy O'Hara, handles more flight daily than do the British Isles.

A spokeman for TWA said the airlines has "long reognized the value of familiarization flights and we continue to support the program."

"But there have been occasions when we have not been able to accommodate the controllers' request, most always for operational reasons when the jump seat is occupied . . .," he said, adding that "generally speaking, we have been able to accommodate the majority of requests, which run up to several hundred a month."

At the press confernce, Leyden estimated that only about 500 controllers each year avail themselves of the free familiarization flights.

Leyden said he would not call a slowdwon, which would be illegal, nor could he predict when and if one might come. But he said that given the mood of the controllers, a job action is likely unless the airlines approve the unconditional free international flights.

"They can allow us a free or spend some money burning fuel," he said.