Three jetliners were hijacked to Cuba in separate incidents yesterday, all of them apparently by Cuban refugees.

The unpredecented events made six sky piracies in one week. Only three other hijackings had succeessfully made it to Cuba since 1973.

The first one yesterday involved six men who took over an Eastern Airlines Boeing 727 flight from Miami to Orlando using a flammable can of deoderant and a toy bug. The second occurred aboard a Republic Airlines DC9 on the same route in late afternoon, and the third involved a Delta flight from San Juan, Puerto Rico, to Miami.

The Federal Aviation Administration said the Republic DC9 was taken over on a flight from Miami to Orlando, Fla., and ordered to Havana. Less than a half-hour later, officials said, the Delta Air Lines L1011 jetliner, flying from San Juan, was hijacked and also ordered to Havana.

The Eastern jet returned to Miami in mid-afternoon, and the Republic plane landed in Miami shortly before 11 last night. The Delta jet landed in Miami shortly after midnight.

In Atlanta, FAA officials said the Republic plane, carrying 111 persons, was commandeered at 6:35 p.m. and landed in Cuba at 7:30 p.m.

The Delta jet, with 165 persons aboard, was hijacked at 7:02 p.m., also landing at Havana's Jose Marti airport. The Delta flight would have ended in Los Angeles after stops in Miami, Atlanta and Dallas-Fort Worth, according to Delta spokesman Jim Ewing.

The FAA said the Republic plane was commandeered by three persons. One to three persons who were believed carrying containers of gasoline diverted the Delta jet, the FAA said.

Further details about the methods used were not available.

The first hijacking yesterday ended when the 40 passengers and six-member crew of the Eastern jet were flown safely back to Miami in mid-afternoon after spending three hours at the Havana airport. The six hijackers, all men, were arrested by Cuban officials after kissing some of the women passengers farewell, other passengers reported.

Ramon Losada of Venezuela, a passenger who acted as translator between the crew and the hijackers, said the six men had told him, "they didn't feel happy here . . . Cuba is the most beautiful land in the world." The men had said they wanted to rejoin families they had left behind.

The piracies occurred as FAA officials, alarmed at the resurgence of skyjackings, were implementing the "hijacker profile" scans abandoned in 1973 when metal detectors were placed at airports.

The detectors and the use of armed guards have all but eliminated pistol and knife-wielding hijackings, which reached a peak of 40 in 1969. Only one attempt involving a pistol has occurred since 1973 (in January of this year), according to the FAA. The 40 other attempts since then have involved flammable liquids, toys, fake bombs or sheer bluff.

Yesterday's Boeing 727 hijackers fingered a toy "Doodle-Bug" radio and waggled its metal antennae saying it concealed a bomb. FBI agent William Nettles said. Another held a can of deoderant and announced that the flammable liquid would be ignited, while others held two bottles of unidentified clear fluid and called it gasoline, the FBI said.

The six men hijacked the plane two minutes after it took off for Orlando.

"We've been passing the word on this [hijacker profile] program since Friday but we just hadn't had time to get it all in place this morning," said FAA spokesman Fred Farrar.

First used in 1972, the profile consisted of a check of boarding passengers by airline employes trained to look for certain characteristics. It has been slightly modified since 1972, Farrar said, and, to preserve secrecy, is nowhere written down.

If a passenger seems to fit the profile, FAA rules allow the airline to ask the passenger to submit to a physical search and to deny boarding rights if the passenger refuses.

Guards and metal detectors were substituted in 1973 "because in the long run they work better," Farrar said. A $28 million "sky marshals" program involving 1,500 armed airline employes posing as passengers on domestic flights also was phased out when the detectors arrived.

In the first six months, the detectors found 17,233 pistols and knives on passengers nationwide. In the first six months of 1979, Farrar said, only 990 firearms and 59 "other" weapons were found in checking 285.7 million persons.

The plummeting skyjack rate also was attributed to a cooperative and tough response from the Cuban government, which has continued to arrest and jail all hijackers despite abrogating a treaty on the subject in 1976.

At Tampa International Airport late yesterday, four Cubans who came to America in the refugee boatlift were arrested on conspiracy charges for allegedly trying to board an Eastern flight to Miami with four quart containers of gasoline hidden in a carry-on bag. The gasoline was found by security officers who searched the bag, which was filled with laundry.

And in Miami last night, Nettles told the wire services that the FBI was concerned that more of the 118,000 Cubans who came to the United States this spring and summer might try skyjacking as a way to get home.

"The problem we're faced with is that there are a lot [of refugees] that want to go back," Nettles said. Tighter security might help, he said, "but in this society we can't have a 100 percent foolproof security system."

This last week's resurgence was unequaled since four attempts were made in four days in 1972. Last Wednesday and Thursday, hijackers threatened to ignite containers of gasoline in order to divert Air Florida and National Airlines jet to Havana. Last Sunday, another pirate used a bar of soap he said was a bomb to hijack another Air Force flight.

All those hijackers were arrested in Cuba and the passengers were returned safely to Miami.