More than 1,700 US flights were cancelled and some 8,000 delayed, the FlightAware website says.
At least two people were killed, hundreds of thousands of premises were left without power and thousands of flights were cancelled or delayed after intense storms lashed much of the eastern United States.
Millions of people on Monday were under severe weather alerts, including tornado watches, as rain, strong winds and hail swept east along nearly the entire eastern seaboard, from Alabama to New York.
The National Weather Service (NWS) had predicted a “moderate risk” of hazardous storms, with gusts up to 80 miles per hour (130kmph).
“Stay weather aware and make sure you have multiple ways to receive warnings,” the NWS in Baltimore and Washington, DC said on social media earlier in the day.
The storms’ spread was massive, with tornado watches and warnings posted across 10 states from Tennessee to New York. The NWS said the area of greatest concern centred in the Washington-Baltimore region.
As much of the severe weather danger subsided into the late evening, some areas faced flood threats as it continued to rain.