FILE PHOTO - A West Jet Boeing 737-700 aircraft (L) departs Vancouver International Airport in Richmond, British Columbia February 9, 2011. REUTERS/Andy Clark

MONTREAL (Reuters) - WestJet Airlines, Canada’s No. 2 carrier, is experiencing delayed and canceled flights and expects “further delays and possible cancellations if more constraints are placed” on the U.S. air traffic system, a spokeswoman said on Friday.

Hundreds of flights were grounded or delayed at New York-area and Philadelphia airports as more air traffic controllers called in sick on Friday, in one of the most tangible signs yet of disruption from a 35-day partial shutdown of the U.S. government.

“We are responding to the situation as required to keep our guests moving,” said WestJet spokeswoman Lauren Stewart by email.