Airlines had scrapped 367 flights on Tuesday and 1,748 on Wednesday across the United States, according to flight-tracking website Flightaware.com.
About 1,800 flights within, into or out of the United States were delayed on Tuesday, Flightaware.com data showed.
Hurricane Ian entered the US Gulf of Mexico on Tuesday and is forecast to become a dangerous category 4 storm over the warm waters of the Gulf, according to National Hurricane Center forecaster Eric Blake.
It is expected to bring hurricane-force winds of up to 130 mph (209 kph) and as much as 2 feet (0.6 meter) of rain to the Tampa area starting early on Wednesday through Thursday evening.
Both Tampa and St. Pete-Clearwater airports in southwest Florida halted operations on Tuesday, while the Sarasota Bradenton Airport will suspend operations at 8 p.m. and Orlando Airport will cease operations at 10:30 a.m. Wednesday.
Walt Disney said on Tuesday it would close its Orlando theme parks on Wednesday and Thursday.
Even Florida airports not closing were experiencing major impacts. Airlines canceled about 40% of flights at Miami International Airport on Wednesday.
Airlines shutting down their flights
Florida is a major part of US aviation and some airlines like JetBlue Airways and Southwest Airlines typically expect 40% or more of their daily flights touch a Florida airport.
Through Tuesday afternoon, JetBlue has canceled 24% of its US flights on Wednesday, while Southwest has canceled 9%.
Southwest suspended operations on Tuesday in Havana, Cuba, and is suspending operations at some Florida airports.
The Federal Aviation Administration said it was "closely monitoring" Hurricane Ian and its path.
Major US carriers also halted some operations.
American Airlines issued a travel alert for 20 airports in the western Caribbean and Florida waiving change fees for ticket booked by Sept. 23.