Irene is gone, and East Coast airports have reopened. But it will take at least several days to get hundreds of thousands of travelers stranded by the storm to their final destinations.
Behind the scenes, ground crews worked through the night to get planes ready, air traffic controllers prepared for a deluge of takeoffs and landings and extra pilots and other employees were called into action.
Airports in New York, Boston and Philadelphia bustled Monday after being closed for part or all of the weekend. The week before Labor Day is always a busy one for airlines, so they struggled to cram travelers stranded by Irene onto already-packed planes.
To make matters worse, more than 1,600 flight were cancelled Monday, adding to the nearly 12,000 grounded this weekend, according to flight tracking service FlightAware. The service estimates that 650,000 passengers have been stuck on the ground since Irene hit, but some experts think it's a million or more.
For airlines, restoring service in three major East Coast cities required a lot of scrambling.
American Airlines pilot Sam Mayer on Monday flew a 757 back to its home New York from Orlando, Fla., where it had been grounded for two days.
It was a full flight.
"We left a lot of people at the gate that couldn't get on," Mayer said.
When a huge storm hits, airlines don't have full control over when they fly. Airports close, mass transit shuts down, roads get blocked _ all creating a situation where the airline might not have any passengers, or might not be able to fly even if the weather at the airport isn't bad yet.
Planes were parked this weekend at airports from California to Orlando. JetBlue had to move more than 50 planes _ a third of its fleet _ away from its home base in New York. Finding extra space for those planes meant dividing them up among more than two dozen airports.
"We had airplanes stacked up like cordwood," JetBlue CEO Dave Barger said in an interview with CNBC.
Duane and Jackie Skene of Jackson, Mich., were supposed to return from a vacation at an Italian resort on Sunday morning, but their flight to New York was canceled. They stayed with friends in Germany and got on another flight to New York early Monday. But they had trouble booking a connecting flight to Detroit.
"We thought we were going to sleep in JFK tonight," Duane Skene said.
It turned out they were on an earlier Delta flight that arrived on time in Detroit Monday afternoon.
"I was anxious until I was sitting on the plane," Jackie Skene said.
Some passengers opted for other means of travel.
Joseph McCann, 22, of Northern Ireland, flew into Philadelphia with a friend on Monday morning. From there, they were supposed to catch a connecting flight to Newark, N.J., but the flight was canceled. He took a bus instead, arriving about 5 hours later than originally scheduled.
Stephanie Neppl, 36, of Auckland, New Zealand, was frustrated with United Airlines for grounding her flight from Chicago to New York on Friday, delaying her trip to watch the opening rounds of the U.S. Open. Neppl had planned the trip so she could watch all four major tennis tournaments in one year, having already been to Wimbledon, the French Open and the Australian Open earlier this year.
"At this stage, Thursday is the earliest I can get there because of restrictions and the airport being closed all weekend," said Neppl, who was watching the opening rounds on TV instead of live. "I'm sitting in my parents' house in Iowa just trying to see if I can get to New York and it's just bloody impossible."
Meanwhile, Amtrak says it's not clear when service will return along the Northeast Corridor between Boston and Philadelphia after Hurricane Irene. Floodwaters remained Monday on the tracks in Trenton, N.J., used by Amtrak and commuter trains.
Spokeswoman Danelle Hunter says the rail line is also dealing with power issues in some areas. And crews worked Monday afternoon to remove trees and other debris that got pushed on the tracks by Irene.
Hunter says trains are running as usual between Washington and Philadelphia.
The storm is expected to cost U.S. airlines $200 million in revenue _ between lost flying and ticket-change fee waivers. Airline officials estimate it will take about two days to get every plane and crew member back in place.
"The next couple of days are going to be trying," said Mike Flores, a US Airways flight attendant and union president. "Once we get to work we're going to be dealing with a lot people who have been up for 24 hours, camped out in airports."
AP Writers Scott Mayerowitz in New York, David Koenig in Dallas, Joshua Freed in Minneapolis, Tom Krisher in Detroit and Kathy Matheson in Philadelphia contributed to this report.