*

FAA mandates flight cuts at 40 major airports due to

safety

concerns

*

Thanksgiving travel disruptions could impact U.S. economic

growth, Hassett warns

*

Airlines for America reports 4 million passengers affected

since

shutdown began

(Updates number of flight cancellations/delays)

By David Shepardson and David Ljunggren

WASHINGTON, Nov 9 (Reuters) - Airlines canceled more

than 2,700 U.S. flights on Sunday and Transportation Secretary

Sean Duffy warned air travel will fall to a "trickle" in the

run-up to the Thanksgiving holiday as air traffic control

staffing shortages surge during the federal shutdown.

Major airlines were dealing with a third day of

government-mandated flight cuts after thousands of delays and

cancellations snarled traffic on Saturday. The shutdown, which

has reached a record 40 days, has led to shortages of air

traffic controllers who, like other federal employees, have not

been paid for weeks.

"It's only going to get worse... the two weeks before

Thanksgiving, you're going to see air travel be reduced to a

trickle," Duffy said on CNN's "State of the Union" program.

Millions of people usually travel in the run-up to

Thanksgiving, one of the most important U.S. holidays, which

this year falls on November 27.

"Many of them are not going to be able to get on an

airplane, because there are not going to be that many flights

that fly if this thing doesn't open back up," Duffy said.

Sunday's cancellations were the single worst day for flight

cancellations since the shutdown began on October 1.

DAILY FLIGHTS CUT

The Federal Aviation Administration instructed airlines to

cut 4% of daily flights starting on Friday at 40 major airports

because of air traffic control safety concerns. Reductions in

flights are mandated to reach 6% on Tuesday and then hit 10% by

November 14.

Many airlines have already planned their cancellations for

the coming days. United Airlines, for example, will cut 190

flights on Monday and 269 on Tuesday, the company said.

As of 9:45 p.m. ET (0245 GMT) on Sunday, data from

flight tracking site FlightAware indicated there had already

been 2,762 U.S. flight cancellations and more than 9,900 delays

as conditions looked to be worsening. The Federal Aviation

Administration earlier in the day said it had staffing issues at

12 towers.

A growing number of air traffic controllers have retired

since the federal shutdown started on October 1, Duffy said. The

FAA is 1,000 to 2,000 controllers short of full staffing, he

told CNN.

"I paid experienced controllers to stay on the job and not

retire," Duffy said. "I used to have about four controllers

retire a day before the shutdown, ... now up to 15 to 20 a day

are retiring."

Some 1,550 flights were canceled and 6,700 were delayed on

Saturday, up from 1,025 cancellations and 7,000 delayed flights

on Friday.

Airline officials privately said the number of delay

programs made it nearly impossible to schedule and plan many

flights and expressed alarm about how the system would function

if staffing issues worsen.

The impact on air travel could hit U.S. economic growth,

White House economic adviser Kevin Hassett said in an interview

that aired on Sunday.

"Thanksgiving time is one of the hottest times of the year

for the economy... and if people aren't traveling at that

moment, then we really could be looking at a negative quarter

for the fourth quarter," he told the CBS show "Face the Nation".

Airlines for America, which represents major carriers, said

staffing issues had disrupted more than 4 million passengers'

travel plans since October 1, when the shutdown began.

By next Friday, it estimated a daily U.S. economic impact of

$285 million to $580 million.

The cuts, which began on Friday morning, include about 700

flights from the four largest carriers: American Airlines ( AAL )

, Delta Air Lines ( DAL ), Southwest Airlines ( LUV ) and

United Airlines.

During the shutdown, 13,000 air traffic controllers and

50,000 security screeners have been forced to work without pay.

Duffy had earlier said he could require 20% cuts in air traffic

if more controllers stop showing up for work.

Republican U.S. Senator Ted Cruz of Texas said he was told

by the FAA that since the shutdown started pilots have filed

more than 500 safety reports about mistakes made by air traffic

controllers because of fatigue.