Trans World Airlines Inc. said yesterday it will cut in half its service to Europe and furlough approximately 2,500 employees in response to a raft of cancellations from travelers nervous about flying while there is a war in the Middle East.

For airlines across the country this week, reservations are down, cancellations are up, lines are long -- and analysts who follow the industry say it probably will get worse before it gets better.

TWA is the first major carrier to announce substantial disruptions in flight schedules, but others may be forced to follow rather than continue flying half-empty planes, according to industry executives. In some cases, the planes and some pilots are being diverted to help ship equipment and forces to the Persian Gulf.

"I think you will see a very sharp reduction in international operations because you just can't keep flying empty aircraft forever," said Julius Maldutis, an airline analyst for Salomom Brothers Inc. in New York. "Even afterwards, it'll take some time to build back up consumer confidence."

TWA said in a brief statement that its "European bookings have fallen to all time low levels." In response, the airline will decrease the frequency of its flights to European destinations and replace larger airplanes, such as Boeing 747s, which carry about 400 passengers, with smaller planes, such as 767s, which carry less than 200. TWA characterized the scheduling changes and the employee furloughs as temporary, but gave no indication when normal operations might resume.

Other airlines report that travel is slow to Europe, but add that January and February are typically the slowest months of the year for transatlantic travel.

At American Airlines, where European flights were about 65 percent full earlier this month, those same flights "are down well under half-full right now," said Tim Smith, a spokesman for the airline. "This trend has really shown up more noticeably since Wednesday or Thursday of last week."

But Smith was quick to note that the market is generally weak: "It's a little hard to separate concerns about war with {concerns about} the economy."

Although Pan Am Corp. has canceled some flights to provide aircraft to the miliary, it has not canceled any flights because of reduced passenger traffic, said spokesman Alan Loflin.

Pan Am reduced its capacity in Europe by about 20 percent last fall, in response to the soft economy, and suspended service to locations in the heart of the Middle East conflict, including Tel Aviv and Riyadh. As a result, "we were better positioned to absorb this ... weak demand," said Jeff Kreindler, another spokesman for the airline.

Several major corporations have added to the slow travel market by pulling back on plans to send their employees abroad. In a drastic move, Corning Inc. has put a ban on all airline travel for its employees, while Minnesota Mining and Manufacturing Co. has canceled all overseas travel and Eastman Kodak Co. has done away with travel to Europe. Other firms, such as American Telephone & Telegraph Co. and General Electric Co. have warned their employees to be cautious about travel and look for alternatives, such as teleconferencing.

Delta, USAir, United and Northwest airlines all are reporting that transatlantic traffic is down, and, like other airlines, they are often waiving standard penalties for travelers who want to reschedule. None of those airlines is canceling flights, however.

The fact that traffic is down may be a blessing for those travelers continuing with their plans: Along with the war has come an increase in security, which means long lines at airports. All curb-side check-in stations have been closed by the Federal Aviation Administration, baggage is being thoroughly screened, often by hand, and American citizens must now go through immigration when returning to this country.

Yesterday afternoon, the average line at the USAir and American check-in counters at National Airport was 40-people long. A tape played repeatedly in the background asking travelers not to leave their bags unattended, as they will be taken for inspection.

While most of the airlines are recommending passengers arrive an hour early for their flights, those working and traveling at National Airport yesterday had different advice.

"We definitely are busier yesterday and today. The lines have been out the door," said Suzanne Anderson, a ticket agent for American Airlines. "An hour, I don't think, is sufficient."

Analysts who follow the airline industry agree that the war puts a new burden on an already beleaguered industry that lost as much as $2 billion last year by one estimate. On top of high fuel costs, a slow economy and a slow season, the fear of terrorism is "almost disastrous" for airlines, said John Pincavage, a partner with the Transportation Group, an airline investment bank based in New York.

"What you're going to see is the airlines that are the weakest, Pan Am and TWA, are going to have the most drastic responses," he said. Other airlines, such as American and Northwest, he said, have the cash to support flying half-empty planes until travel picks back up.

Pincavage and other analysts agree that TWA probably is not using the war as an excuse for the financially troubled airline to cut its losses.

"For an excuse, you drop a few flights -- this is clearly a response to having no bookings," said Edward Starkman, airline analyst for PaineWebber Inc. in New York. "The main problem is nobody's traveling. The acid test will be whether they put those services back when the war is over."

Staff writer Robert O'Harrow Jr. contributed to this report.