Most private plane owners would no longer be able to prevent the public from tracking their flights in real time under a new policy being considered by the U.S. Department of Transportation, according to a trade group.

As we reported last year, plane owners can currently keep their flight information secret for any reason by simply having the trade group send a request to the Federal Aviation Administration. While that policy was created for security and competitive business concerns, ProPublica found a number of individuals and companies that signed up for the program after receiving bad publicity.

Among them were a televangelist facing a congressional inquiry, governors who had been questioned about personal trips on state planes, college athletic programs seeking to hide recruiting trips and Fortune 500 companies that had received government bailouts.

Now, the government is considering limiting the program to plane owners who can prove a legitimate security concern, Ed Bolen, president of the National Business Aviation Association, said in a letter posted Monday on the group's website.

When we asked FAA spokeswoman Laura Brown about the letter, she said only that the agency is "reevaluating" the program. The letter, and the potential policy change, were first reported Monday night by Politico.

Use of the national airspace is generally considered public information because pilots -- whether airline captains or recreational fliers -- rely on a system of air traffic controllers, radars, runways and towers that are paid for or subsidized by taxpayers. As a result, flight data is collected by the FAA in its air traffic control system.

The program allowing owners to block the information was created in 2000 after private plane groups complained to Congress about a number of websites posting real-time government data of planes' locations and flight schedules.

A measure attached to an FAA reauthorization bill that year required websites that use the data to exclude any aircraft upon FAA request. But over the years the process has changed with the business aviation association telling the FAA and websites which planes to take out of the system.

Plane owners have two options for keeping their flights secret. In one, the aviation association sends a "block" list to the FAA, which removes the planes from data released to the flight-tracking websites. In the other, the trade group sends a list directly to the websites, which are bound by FAA agreement to hide the planes.

ProPublica obtained the FAA version of the block list through the Freedom of Information Act last year after a judge ruled against a lawsuit by the business aviation group seeking to keep the list confidential.

In his letter Monday, National Business Aviation Association's Bolen said the "onerous limitations" could go into effect as early as Feb. 15. As of last month, however, the group stopped accepting new block requests. He said the group has conveyed its concerns directly to Transportation Secretary Ray LaHood and have requested another meeting with him this week.

It's unclear if the government is considering the group's argument that disclosure of flights could jeopardize business deals and affect stock prices. But the group does seem to be focused on how the exemption for security will be granted. It recently sent its members a survey asking them if they had employees who qualified under Internal Revenue Service rules to receive a tax deduction for employer-provided transportation for security concerns.

The IRS rules use a strict standard requiring a specific "business-oriented security concern," such as a threat of death or kidnapping or a recent history of terrorist activity in the area where the employee is working. To qualify for the deduction, the employee must have an overall security program in which bodyguards or chauffeurs are provided on a 24-hour basis when the employee is both at work and at home.

Update (5 p.m.): We just heard from the National Business Aviation Association and the group said it is now continuing to process requests to block planes.