The U.S. government has a specialized plane loaded with advanced sensors that officials brag is always ready to deploy within an hour of any kind of chemical disaster. But the plane didn’t fly over eastern Ohio until four days after the disastrous Norfolk Southern derailment there last year.

A whistleblower told The Associated Press that the Environmental Protection Agency’s ASPECT plane could have provided crucial data about the chemicals spewing into the air and water around East Palestine as the wreckage burned and forced people from their homes.

The man who wrote the software and helped interpret the data from the advanced radiological and infrared sensors on the plane said it also could have helped officials realize it wasn’t necessary to blow open five tank cars and burn the vinyl chloride inside because the plane’s sensors could have detected the cars’ temperatures more accurately than the responders on the ground who were having trouble safely getting close enough to check.

But the single-engine Cessna cargo plane didn’t fly over the train crash until a day after the controversial vent-and-burn action created a huge plume of black smoke over the entire area near the Ohio-Pennsylvania border.

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Robert Kroutil said even when the plane did fly, it only gathered incomplete data. Then, when officials later realized some of the shortcomings of the mission, they asked the company Kroutil worked for, Kalman & Company, to draft plans for the flight and backdate them so they would look good if they turned up in a public records request, Kroutil said.

Kroutil said his team labeled the mission inconclusive in their report because only eight minutes of data was recorded in the two flights and the plane’s chemical sensors were turned off over the creeks. But he said EPA managers changed the report to declare the vent-and-burn successful because the plane found so few chemicals when it eventually did fly.

“We could tell the data provided from the ASPECT plane’s two East Palestine flights on February 7 was incomplete and irregular. We had no confidence in the data. We could not trust it,” Kroutil said.

The revelations about the use of the ASPECT plane in the aftermath of the worst rail disaster in a decade raises new questions about the effectiveness of the “whole-of-government response” in East Palestine the Biden administration touts.

The Government Accountability Project that represents Kroutil and has been critical of EPA’s response in East Palestine sent a sworn affidavit detailing his concerns to the EPA inspector general Tuesday and requested a formal investigation. The group provided a copy of the affidavit and Kroutil agreed to an interview with the AP ahead of time.

The EPA said in a statement Tuesday that the agency didn’t even request the plane until Feb. 5 — two days after the derailment — and it arrived in Pittsburgh late that day from its base in Texas. Due to icing conditions, the flight crew decided it wasn’t safe to fly it on the day of the vent-and-burn, but it’s unclear why the plane didn’t make a pass over the derailment on its way into the area. EPA Response Coordinator Mark Durno has also said he believes the agency had enough sensors on the ground to effectively monitor the air and water as the derailed cars burned.

The agency said its “air monitoring readings were below detection levels for most contaminants, except for particulate matter” in the first two days after the derailment and “air monitoring did not detect chemical contaminants at levels of concern in the hours following the controlled burn.” Officials say data gleaned from more than 115 million readings doesn’t show any “sustained chemicals of concern” in the air since the derailment.

But many residents of the town who still complain of respiratory problems and unexplained rashes while worrying about the possibility of developing cancer have doubts about the EPA’s assurances that their town and the creeks that run through it are safe. More than 177,000 tons of soil and over 67 million gallons of wastewater have been hauled away as part of the ongoing cleanup that’s cost the railroad more than $1 billion.

The head of the NTSB has said her agency’s investigation determined the vent-and-burn wasn’t necessary because the tank cars were actually starting to cool off, confirming that a dangerous reaction wasn’t happening inside them — something the chemical company had tried to tell officials. But the people who made the decision to blow open those tank cars said they were never told what OxyVinyls’ experts determined. Instead, they heard only about the fears the tank cars might explode.

The EPA said the ASPECT plane’s flights in East Palestine were consistent with past missions, but that doesn’t match Kroutil’s experience.

“The East Palestine derailment was the oddest response I ever observed with the ASPECT program in over two decades with the program,” said Kroutil, who helped develop the program when he worked for the Defense Department after the 9/11 attacks prompted fears about chemical explosions.

Kroutil said he retired in frustration in January and wants to share his concerns about the East Palestine mission. He said this incident was handled differently than the 180 other times the plane has been deployed since 2001. Some of those times, the plane was even sent out as a precaution to be nearby political conventions and Super Bowls just in case something happened.

“You want to fly over a train derailment in the first five to 10 hours after the incident and while the fires are still burning. It is really advantageous if you have a plume. That big black plume ... is when you want to get in and collect data,” Kroutil said. “The EPA ASPECT airplane should have made passes over the derailment site right away but certainly before the vent-and-burn. I think they chose not to know.”

Kroutil’s former boss, Rick Turville, is the program manager for the ASPECT plane data interpretation at Kalman. He said he trusts Kroutil completely because he is one of the world’s preeminent experts in spectroscopy and he shares his frustration about the plane not flying sooner. The experts Kalman employs could see the news reports about the disaster in East Palestine but couldn’t act until the EPA deployed the plane.

“These kind of fires or refinery fires, fertilizer plant explosions, they don’t happen often,” Turville said. “But when they do, you got to be there and you got to be there quick. And that’s how you save lives.”

Fortunately, no one died in East Palestine but thousands of lives were upended after the derailment and the worries about future health problems won’t go away.

The EPA manager in charge of the program, Paige Delgado, didn’t immediately respond to an email sent to her Monday with questions about her actions.

Kroutil said he heard Delgado order the plane’s operator to shut down the chemical sensors when it flew over the creeks in East Palestine even though officials were concerned about chemicals reaching those waterways, potentially fouling drinking water supplies downstream on the Ohio River. Kroutil said his satellite link to the plane’s instruments confirmed those sensors were turned off.

The EPA’s official report on the two East Palestine flights does describe pictures the plane took over Little Beaver Creek after a problem with its aerial camera was fixed, but it doesn’t mention Sulphur Run that flows right next to the derailment site or the bigger Leslie Run creek that flows through town.