Trans World Airlines Inc. Chairman Carl Icahn said yesterday that he may sell or break up the airline if machinists in Kansas City, Mo., and New York refuse to cross the picket lines established by the airline's 5,700 flight attendants.

Icahn said that, although more than half of TWA's regularly scheduled flights operated yesterday, the airline is experiencing problems in New York and Kansas City, where many members of the International Association of Machinists and Aerospace Workers are refusing to cross the picket lines. TWA does almost all of its long-term airplane maintenance in Kansas City, while New York's Kennedy Airport is the departure point for TWA's flights to Europe.

"If the machinists continue to honor the picket lines, we unfortunately might be forced to sell the airline," Icahn said in a telephone interview. "All of the other employe groups have been really terrific. We will have no trouble unless the machinists continue to honor the picket lines, which could lead to the sale or breakup of the airline."

Machinists officials said the union is leaving the decision of whether to cross the flight attendants' picket line up to individual members. Meanwhile, TWA asked a federal judge in Kansas City yesterday to force the machinists to go back to work, but there was no ruling.

When Icahn said "breakup of the airline," he was referring to the possibility that various TWA assets could be sold to the highest bidders. Industry analysts said American Airlines is interested in buying TWA's overseas routes, Delta Air Lines might be interested in its St. Louis hub operation, and Northwest Airlines and others might like to buy TWA's valuable PARS reservation system.

As the strike, which began early Friday morning, ended its fourth day, TWA officials said the airline operated 54 percent of its regularly scheduled flights. The airline said it expects to operate 61 percent of its normal flights today. The flight attendants union disputed the 54 percent figure, saying TWA's flights have been cut back to only 20 percent of normal.

In Washington, TWA operated 8 of 21 regularly scheduled flights from Washington National and Dulles International airports, and 3 of 5 flights from Baltimore-Washington International Airport. TWA said it operated two of 14 regularly scheduled flights out of New York's LaGuardia Airport.

TWA and the flight attendants said they plan to resume negotiations over wages and work rules on Wednesday morning in Philadelphia. Icahn said yesterday that, when unsuccessful talks ended early Friday morning in Washington, he was asking the flight attendants to take a 17 percent cut in wages and work several additional hours a week. The financially troubled airline said its machinists recently agreed to a 17 percent cut in pay, while the airline's pilots agreed to a 26 percent pay cut.

The striking flight attendants have been replaced by 1,500 new hires and 1,500 supervisors. Icahn said yesterday that, even if the striking flight attendants return to work, they will not replace the new hires, who are earning salaries of about $1,000 a month, far below the average $35,000-a-year salaries of the striking flight attendants.

"We offered [the flight attendants] 17 percent pay cuts plus new work rules," Icahn said. "We certainly cannot afford to go any lower than that."

Officials of the machinists and flight attendants unions said yesterday they believe the safety of TWA's flights is jeopardized by the strike. They said airplane cabin safety has been reduced because the new hires lack the training of the strikers, and airplane safety has been hurt because the supervisors and others who have replaced the machinists lack the necessary skills to service TWA's airplanes.

Wall Street analysts expect the machinists in New York and Kansas City to go back to work soon.

"In any strike, if the employes cannot shut the airline down, they might as well go back to work," said E. F. Hutton analyst Hans Plickert. "My own feeling is that, if TWA was able today to get 50 percent of their flights into the air, then the strike will be difficult to maintain."