From CNBC:

Over 320 flights canceled due to winter storm at Denver International Airport. More than 2,000 U.S. flights canceled on Tuesday due to winter weather disrupting travel for millions. Northeast storms cause nearly 6,000 delays and snarled operations at major airports. New York and Washington, D.C. saw significant snow accumulation. Major airlines allow travelers to change flights without paying fare differences. NYC, Newark, and Reagan airports see high percentage of flight cancellations or delays. Southwest Airlines had most delays of any U.S. carrier, with about 1,000. Airlines also canceled or delayed about 30% of flights at Denver International Airport. Boeing 737 Max 9 grounding also contributed to cancellations and delays for Alaska and United airlines. Both airlines waived change fees for affected travelers.



Read more: Flight disruptions linger amid winter storms, Max 9 grounding