The AP traced at least 50 aircraft back to the FBI, and identified more than 100 flights in 11 states over a 30-day period since late April, orbiting both major cities and rural areas. At least 115 planes, including 90 Cessna aircraft, were mentioned in a federal budget document from 2009.
For decades, the planes have provided support to FBI surveillance operations on the ground. But now the aircraft are equipped with high-tech cameras, and in rare circumstances, technology capable of tracking thousands of cellphones, raising questions about how these surveillance flights affect Americans' privacy.
"It's important that federal law enforcement personnel have the tools they need to find and catch criminals," said Charles Grassley, chairman of the Senate Judiciary Committee. "But whenever an operation may also monitor the activities of Americans who are not the intended target, we must make darn sure that safeguards are in place to protect the civil liberties of innocent Americans."
The FBI says the planes are not equipped or used for bulk collection activities or mass surveillance. The surveillance equipment is used for ongoing investigations, the FBI says, generally without a judge's approval.
The FBI confirmed for the first time the wide-scale use of the aircraft, which the AP traced to at least 13 fake companies, such as FVX Research, KQM Aviation, NBR Aviation and PXW Services.