Wind power may be flying high, but the young industry fears its growth may be clipped if federal rulemakers and Congress continue to set up new regulatory hurdles.

At the industry's recent annual conference here, one of the topics under discussion was the federal government's intensified interest in checking the height of wind power turbines to make sure they don't interfere with military radar. Until now, the industry pretty much concentrated on fending off criticism about the danger the fast-moving turbine blades can present to bats and birds, as well as the turbines' noise and unsightliness.

But in January, Congress mandated a study of the effects of proposed wind turbines on military operations, including aircraft radar, triggering special scrutiny by the Federal Aviation Administration and the Department of Defense.

The perceived military problem is that the tall turbines might create false signals picked up by military radar.

As the process now works, Defense can weigh in, but after reviews are complete, the FAA makes the final decision.

Turbine developers say the inspections are holding up projects and putting them in financial peril. They say the delays may interfere with the president's goal of having wind power account for 20 percent of the nation's electrical generation by 2008.

FAA spokeswoman Laura Brown said the process is taking longer because growth in the industry has been exponential, with wind turbines in 30 states and only 12 FAA staffers to do the work.

In 2004, the FAA had 1,900 proposed turbine projects; this year, it has 5,000 so far. "And 360 just came in the door yesterday," Brown said. She said that the review process usually takes about a month and that 2,200 turbine proposals have been approved this year.

Horizon Wind Energy, a Houston firm owned by Goldman Sachs, has plans to put up a wind facility in Bloomington, Ill. In April, the company got a letter from the FAA saying the wind farm might pose problems. Michael Skelly, Horizon's chief development officer, said the company started working with the FAA immediately but never really found out what the military issues were. On May 25, the FAA approved the project.

The study requirement was added to the 2006 Defense Authorization Act and is widely viewed in the industry as a way to stall development of a wind farm on Nantucket Sound. Sens. John W. Warner (R-Va.) and Edward M. Kennedy (D-Mass.) oppose that project, which the FAA has already approved.

What really shook up the industry was a March 21 directive from the Defense Department and the Department of Homeland Security that said "any establishment of windmill farms within radar line of sight of the National Air Defense and Homeland Security Radars" would be contested.

Until then, the evaluation centered mostly on how tall structures -- radio towers, turbines -- would affect military air space and training routes as well as landings at commercial airports.

Lt. Col. William Crowe, chief of air space policy for the Air Force, said in an interview that the Defense/DHS Long Range Radar joint program office at Langley Air Force Base, which worries about aircraft entering the country illegally, has become concerned about whether the turbines create false signals or cause other interference in the radar's line of sight.

Crowe said the military wants to do an early evaluation of sites before the FAA review process even begins. "We want to get in early and tell them if it's in a certain area, it won't work," he said.

Laurie Jodziewicz, policy specialist for the American Wind Energy Association, the industry's trade group, said wind power has peacefully coexisted with radar for some time. She said that on occasion, the solution has been to move or lower towers.

Some military installations have operating turbines, including the U.S. Navy base at Guantanamo, F.E. Warren Air Force Base in Wyoming and an Air Force base on Ascension Island.

The industry is anxious about any delay in construction because a federal tax credit to build wind farms expires at the end of 2007.

But Jodziewicz said developers who receive a "Notice of Presumed Hazard" from the FAA cannot get financing or go forward with construction.

The industry is particularly worried about 12 projects in Wisconsin, Illinois, and North and South Dakota where developers got such letters.

The FAA said the impression that projects, especially in the Midwest, will be permanently derailed is unwarranted.

John Calaway, chief executive of Superior Renewable Energy in Houston, got a "presumed hazard" letter three months ago concerning a project in South Dakota, but it was recently cleared by the FAA. He also had to move towers five miles down a ridge to get clearance from the Defense Department on a project in San Diego County in California.

Calaway said the experience taught him, and should send a signal to the industry, that the radar issue should be up on their screens.

"The FAA used to be the last thing we checked off. The lesson now is that this is not a guaranteed, rubber-stamped deal. We probably should have been paying more attention to radar."