As hazardous air sweeps into the east coast from the Canadian wildfires, travelers should monitor their carrier’s guidance as conditions are anticipated to continue over the next several days.

On Thursday morning, Dallas-based Southwest Airlines said “there were no major operational issues to report,” but was monitoring the situation to make adjustments as necessary. Southwest flights in the Northeast were arriving and departing in Northeast cities.

As of 9 a.m., there were no cancellations due to air quality at DFW International Airport or Dallas Love Field, according to FlightAware.

United Airlines said the carrier is also monitoring the situation, checking on employees’ safety who work outside. United has waivers in place for customers traveling to, from or through affected airports. Travelers can reschedule their trip with United and the airline will waive change fees and fare differences.

Residents from Massachusetts to North Carolina are advised to wear masks and limit time outdoors. Dense smoke traveled to New York City on Wednesday, causing a orange tinted sky. At 9 a.m. on Thursday, Newark International Airport and LaGuardia Airport were at ground delays due to “low visibility,” according to the National Airspace System Status.

In North Texas, the National Weather Service has issued an air quality alert until Thursday evening, citing a combination of particle pollution and increased ozone levels as responsible for the current air quality.