When the monitors that hang from the ceiling begin to shake, air traffic controllers in the 398-foot tower at Atlanta’s Hartsfield-Jackson International Airport know a fierce wind is blowing outside.

On Wednesday, as their tower swayed, they also knew that 2,700 flights were scheduled to arrive or depart from the nation’s busiest airport during a massive blast of bad weather that spawned several killer tornadoes.

The problems in Atlanta overnight and the turmoil caused as the storm swept north and east Thursday snarled air travel throughout the day and may ripple into Friday before it’s all sorted out.

“It was the worst I’ve ever seen it,” said Rob Thorne, a controller who has worked the Atlanta tower for five years.

The problem wasn’t just the swirling winds but the direction from which they came. Planes can land in strong winds, but when those winds come at the airfield from right angles they pose a danger too great.

“They were 25-30 knots, gusting as high as 47, I saw once,” Thorne said.

The turbulence of a post-tornado atmosphere makes for a jarring, white-knuckle ride for passengers, and tests the skill and judgment of pilots and controllers.

“There were periods of time when they could land, but we had at least 40 ‘go- arounds,’ and on a normal day you have one or two,” Thorne said.

For passengers, that means that the end of a bumpy flight is postponed as their pilots are told to break off landing and try a second time.

“We had one [Boeing] 757 making his third approach, and he wanted to see if he could make it in, but at about five miles he had to break off and divert to Charlotte,” Thorne said.

Dozens of planes, running too low on fuel to circle the airport, were sent elsewhere. Normally, the 11 p.m. final push to get the last planes in the air brings near-quiet to the Atlanta field, but when Thorne signed out at midnight, every inch of tarmac was packed with planes that had been unable to get airborne.

“I heard it was 4 a.m. before they got them cleared out,” he said.