Spurred by increasing complaints about “low-flying” jets, members of a noise committee Tuesday pressed the city to take a hard look at whether planes are flying into O’Hare Airport at lower than normal altitudes.

Bensenville Mayor Frank Soto urged the city to tease out the “anomalies” of planes that might be flying below a standard glide path altitude into O’Hare.

“Things get lost in the averages,’’ Soto told the Technical Committee of the O’Hare Noise Compatibility Commission.

“That’s not what keeps people up at night. We need the anomalies” from as many as 10 miles outside O’Hare, Soto said.

Chicago Department of Aviation officials said they could work up an analysis but did not want to make judgment calls about a plane’s altitude.

“We are happy to help you with your data,” Assistant Aviation Commissioner Aaron Frame said. “But just a caution. We are not the altitude police.”

A plane’s altitude, Frame said, is “a federal issue.”

Wednesday’s comments came during discussion of a chart showing the standard “3-degree glideslope” approach into O’Hare and deviations from it during an unspecified “average day of arrivals” on Runway 27L. That runway, which is roughly parallel with Thorndale Avenue, was the most heavily used by arrivals over Chicago in July.

This chart shows the standard glide path and altitudes of planes approaching heavily used Runway 27L at O'Hare. Source: Chicago Department of Aviation

This chart shows the standard glide path and altitudes of planes approaching heavily used Runway 27L at O’Hare. Source: Chicago Department of Aviation

The chart indicated that at 12 miles from the runway’s end, altitudes varied by up to, roughly, 800 feet.

“Eight hundred feet makes a big difference,” Wood Dale Ald. Art Wood said.

But 5 miles away, where planes are supposed to hit a “final approach fix” altitude of 1,600 feet and join an aerial queue headed into O’Hare, deviations were far less frequent.

Ald. John Arena (45th) noted that 28 percent of all July O’Hare jet noise complaints to the city were about “low-flying” planes. In June it hit 32 percent. That compares with 17 percent in July 2013, a few months before O’Hare flight paths changed dramatically as part of an ongoing airfield overhaul.

During that same time period, spurred in part by a user-friendly citizen-created website that forwards complaints to the city’s official site, O’Hare jet noise complaints have skyrocketed from nearly 2,300 complaints by just over 600 people in July 2013 to more than half a million complaints by more than 90,000 people in July 2016.

Arena said he would like to see a breakdown of anomalies at each mile, as far as 12 miles out.

“Any time we’ve talked about this with the [Federal Aviation Administration], they say it’s not happening,” Arena said. “If that’s the case, prove the case.”

Soto said that “drilling down on anomalies” would allow officials, and the Technical Committee, to see whether they fall into a pattern of repeated deviations by a particular airline or pilot.

Park Ridge resident Al Rapp, a leader of the Fair Allocation in Runways citizen coalition, asked the committee to also analyze deviating altitudes of departing jets, especially those that he said have been making “extreme” turns over Park Ridge.

“I’ve observed the same aircraft, at much different altitudes visually,” Rapp said. “Call it whatever you like. There are discrepancies.”