In less than an hour this morning, a Center City landmark was transformed, and Philadelphia's skyline along with it.

The building at 1 S. Broad St. was quickly stripped of its iconic "PNB" signs, as a crew atop the 28-story building worked in tandem with a helicopter to remove the letters, each of which weighed one and a half tons.

The giant letters - four sets of PNB on each side of the former Philadelphia National Bank building - had been in place since the 1950s.

"It took an hour this time to remove nine letters - and last time it took four hours to remove three, so they're doing better," a police officer joked as the letters were hauled onto large flatbed trucks to be towed away.

In August, three of the 16-foot letters were removed after building owner Wells Fargo had determined the letters were structurally unsound, and a safety hazard.

But the process was stymied by technical difficulties.

"In the course of the removal last time, it was discovered that where the letters were bolted onto the framework, over time it had corroded into almost a solid unit, and that's what made it so difficult to get them off," Wells Fargo spokeswoman Barbara Nate said.

"This time, armed with that knowledge in advance, much pre-work was done to address that issue and free the joints."

Not everyone was sad to see them go.

Ken Avella, 49, stopped to snap a photo of the denuded skyscraper. He lives in a highrise nearby and watched the helicopter remove the letters from his balcony - with a bit of glee.

"It's such a beautiful Art Deco building and I always thought the letters kind of marred it," he said. "So I'm very happy. I hope they don't put another sign in its place."

Terrence White, 57, of Southwest Philadelphia also stopped to check out the scene - and conceded he felt a bit nostalgic.

"It's been there a long time," he said. "But I guess everything is subject to change."