Flight cancellations have mounted as the government shutdown stretches into its second month, causing headaches for travelers nationwide.

Over 7,000 flights on Sunday "within, into, or out of" the country had been delayed, according to flight-tracking website FlightAware. The number of cancellations for flights "within, into, or out of" the country topped 2,200, the website said.

Airports including Hartsfield-Jackson Atlanta International Airport, Newark Liberty International Airport, Chicago O'Hare International Airport and New York's LaGuardia Airport saw delays in the hundreds Sunday, according to FlightAware.

Republicans and Democrats have been locked in the shutdown fight for over a month, battling it out over health care. But there has been some recent movement. As many as 10 Democratic senators are expected to vote for a bill to reopen the government as soon as Sunday evening or early Monday morning.

On Sunday, Transportation Secretary Sean Duffy said that "15 to 20" air traffic controllers were retiring per day during the government shutdown.

"I used to have about four controllers retire a day before the shutdown. I'm now up to 15 to 20 a day are retiring," Duffy said on CNN's "State of the Union." "So, it's going to be harder for me to come back after the shutdown and have more controllers controlling the airspace."

"So, this is going to live on in air travel, well beyond the time frame that this government opens back up."

Duffy also said on "Fox News Sunday" that Defense Secretary Pete Hegseth had offered air traffic controllers from reserves amid a shortage during the shutdown.

"I had a text from the secretary of War, Pete Hegseth, yesterday, who's made an offer that he has air traffic controllers in the reserves, if we could deploy them -- and I don't know that we can -- we got to see what airspaces they worked in," Duffy told anchor Shannon Bream.

Flight cancellations mount as government shutdown continues