Time was, New Yorkers only concerned themselves with jumbo jets flying into buildings. Now they worry about cranes, as well:

New York has always been a city of construction cranes: They are the steel crutches of the skyline, forever pulling it upward. But when one of them collapsed on the East Side on Saturday — killing at least four people, demolishing a building and damaging at least five others — the disaster exposed the often-uneasy relationship cranes have had with the New Yorkers who walk below them.

Officials said that about 250 cranes were now in operation in the five boroughs, a telling sign of the city’s building boom. Construction cranes are towering behemoths, signposts of the city’s prosperity that dominate the skyline for months but often go unnoticed.

Yet on Sunday, those who lived, worked or happened to be walking near the cranes looked upward with anxiety, their nerves rattled by Saturday’s collapse.

A gas station cashier who works below a crane at West 24th Street and 10th Avenue said he trusted God to protect him. A neighbor who lives across the street, Ana Gonçalves, puts her faith in the builders and hopes they know what they are doing. Victor Simpkins, another neighbor, has watched the crane for weeks, but now he looks up at it with a new suspicion.

“If that thing would fall over, my building would be toast,” said Mr. Simpkins, 53, a designer and filmmaker.

. . .

Mayor Michael R. Bloomberg acknowledged the danger of high-rise construction, but said residents near cranes were generally safe. “Do I think that you should worry if there’s a crane across the street?” the mayor said at a news conference on Sunday. “No. This is such a rare thing that I don’t think we should worry about it.”

But as cranes have proliferated, so, too, have accidents associated with them. Last year, there were eight crane-related “accidents,” up from five in 2006; and 21 crane-related “incidents,” up from 14. As the city’s Department of Buildings defines them, “accidents” involve fatalities or injuries, and “incidents” do not.

The collapse of the 205-foot crane on Saturday — described by city and union officials as one of the worst crane accidents in memory — gave rise to a grim New York City parlor game, one that pedestrians have doubtlessly played in the back of their minds over the years: If that crane fell, where would it hit?

“We thought about it, and we think if it falls, it will probably fall into the park or bounce off that clock tower,” said Jarrod Shandley, 25, who lives with two roommates in a penthouse that looks out onto a crane at East 23rd Street and Madison Avenue.

. . .

Some New Yorkers showed no fear of cranes. Mr. Shandley, who lives in the penthouse, said crane anxiety after Saturday’s collapse was “an irrational fear.” Mr. Shandley, who works for a financial research company, added, “I don’t think you should be any more worried about a crane than crossing the street and getting hit by a cab.”