Chicago ? Mayor Richard Daley sent construction workers under cover of night to tear up the runway of a small airport along the city’s lakefront, saying Monday it was done to help prevent a terrorist attack.

Critics suggested Daley was using post-Sept. 11 fears to pursue his long-held goal of turning the single-runway airport along Lake Michigan into a park.

He said the city would be safer without an airport “within a few hundred yards — and only a second’s flight time — from our tallest buildings.”

The federal government recently granted Daley’s request for a no-fly zone over downtown, but that still allowed low-flying planes to pass near landmarks such as the Sears Tower and other skyscrapers on their way to Meigs Field, which is used primarily by smaller corporate and private planes.

“Those airplanes appear to be going to Meigs, but with a sudden turn they could cause a terrible tragedy downtown or in our crowded parks,” Daley said at a news conference, hours after crews carved huge X-shaped divots in the runway as police kept everyone else off the property.

The move steamed critics, who argue the airport is important to major corporations and actually gives the city added security because workers there monitor planes in the area.