Getting over the river and through the woods to the family Thanksgiving feast via O'Hare International Airport - always a challenge - may be even tougher this year because of new federal flight limits.

And things don't look much better for Christmas, say travel agents, airline and aviation officials."We're routinely advising our customers and clients of the, let's say, congestion problems at major airports, particularly O'Hare," said David Powell, American Express Travel Service vice president.

The new Federal Aviation Administration limits on the number of flights allowed to arrive at O'Hare in a given hour are likely to aggravate the problem at the nation's busiest airport.

Following a startling 150 percent increase in the number of errors by air traffic controllers at O'Hare this year, the FAA in October ordered the airport to cut the number of arrivals from 96 per hour to 80 per hour between peak-travel times of 4:45 p.m. and 9:15 p.m.

While the cutbacks, called a "flow control program," were designed to make skies safer, airlines acknowledge they also have increased tardiness in a system in which delays never were uncommon.

"We have seen a definite impact from the flow control program," said spokesman Tom Stack of American Airlines, the second-largest carrier at O'Hare.

"To give some example, in October of 1987 at O'Hare we were above 95 percent in our arrivals within 15 minutes. That dropped to about 75 percent in October of this year."

Airlines also no longer have a reserve of planes to help accommodate heavy holiday traffic, said United Airlines spokesman Joe Hopkins.

While the number of flights over the holiday won't be up much - about 2,300 total arrivals and departures per day - the number of people in the skies will be, as airlines see their planes filled to capacity.

Stack anticipates that sometime over the four-day Thanksgiving weekend, American will top its previous one-day record of more than 30,000 passengers flown out of O'Hare.

"Passengers ought to look forward to having some delays," both in the air and on the ground, he said, adding that Sunday may be worst of all.

"People can choose a variety of days to begin vacation, but pretty much they wind up returning on that Sunday."