Thomas Frank, USA TODAY
Nobody in the medical helicopter saw the little Cessna airplane as the two aircraft approached Shenandoah Valley Regional Airport in Virginia.
Skies were clear and visibility excellent the afternoon of Dec. 31, 2010. The airport had no air-traffic controllers, forcing incoming pilots to avoid each other using crude technology: their eyes.
At 2:26 p.m., a nurse sitting in the helicopter felt a sudden bump. On the ground, witnesses saw the helicopter barely touch the four-seat Cessna. But the collision severed the Cessna's right wing, sending the plane plunging 500 feet to the ground. The pilot and passenger were killed instantly, marking the 20th collision of that year in the United States.
After a probe of the crash, federal investigators blamed a familiar culprit: the "inherent limitation" of pilot observation, "which made it difficult for the helicopter pilot to see the airplane before the collision."
Starting Sunday, tens of thousands of pilots flying each day will have to rely increasingly on "see-and-avoid" as the Federal Aviation Administration begins to close nearly a third of its air-traffic control towers to cut costs. The 149 affected airports - small facilities in 38 states catering to private and commuter flights - will remain open but without controllers to keep airplanes a safe distance apart and to warn pilots about runway hazards they may not see.
The tower closures are among thousands of steps federal officials are taking to cut $85 billion in spending this year as a 2011 law requires. But unlike furloughs, removing 871 controllers who guide 8 million planes a year around airports raises fears that pilots, passengers and bystanders will be killed.
"You're putting people's lives at risk," said Sen. Jerry Moran, R-Kan., who is trying to restore funding for the control towers, including five in his state. "It's like taking down the stop signs in your town."
A few communities are suing to stop the tower closures, saying the FAA has not done a safety analysis.
U.S. airplane collisions have killed an average of 30 people a year since 1982 - a total of 910 deaths, according to a USA TODAY review of federal records. Another 167 people have been seriously injured, and 729 airplanes have been destroyed or substantially damaged in the collisions, the records show.
Pilots flying around airports without towers are at greater risk, the FAA said in a 1990 paper. At airports with towers, "midair collisions are less frequent, and fewer aircraft are damaged in landing accidents," the FAA wrote in the paper that it used as recently as 2005 to determine which airports need control towers.
The paper says the risk of a midair collision is three times higher around an airport without a control tower than at an airport with a tower. Runway collisions are six times more likely at the "non-towered" airports.
"We wouldn't have built these towers if we didn't believe they provided safety," Moran said.
Transportation Department spokeswoman Sasha Johnson said the FAA paper is no longer used to assess risk and does not reflect safety improvements in the past 25 years.
In its analysis, USA TODAY found that nearly half of the collisions since 1982 occurred at or near non-towered airports. About a quarter occurred around airports with towers, and a quarter occurred far from any airport, in spots where pilots often have no contact with controllers.
Roughly 90% of the nation's 4,880 public airports do not have towers. Typically rural fields with no passenger flights, each has a small fraction of the traffic at major commercial airports with towers.
Transportation Secretary Ray LaHood said in a statement Thursday that the FAA will monitor safety at airports losing controllers and "is committed to maintaining this nation's extremely safe aviation system."
The FAA says it had to close towers to reach the savings required of almost every federal agency under automatic budget-cutting, called sequestration. The 149 towers are all operated under contracts that the FAA can break on short notice, providing $33 million of the $637 million the agency must cut by Sept. 30. The FAA also plans to furlough 47,000 employees for up to 11 days over the next six months.
Other contracts could not be cut because they help run the entire air-traffic-control system, the FAA said. An FAA program that gives airports $3 billion a year in grants for capital projects is protected by a 1985 sequestration law, the Congressional Research Service (CRS) said.
The tower closures will have "relatively small but measurable impacts on safety and efficiency," CRS said.
"Our overall principle has been, How can we protect the maximum number of travelers?" FAA Administrator Michael Huerta told a Capitol Hill hearing in February.
The FAA is closing towers only at airports with fewer than 10,000 commercial flights a year - about 27 per day - and fewer than 150,000 annual arrivals and departures. The closures will not touch the hub and regional airports that handle most commercial traffic, mostly affecting people who fly private planes for business or recreation.
Towers will go dark at 36 airports where small planes operate next to scheduled passenger flights, in cities such as Winston-Salem, N.C., La Crosse, Wis., and Branson, Mo. About 3 million passengers used those airports in 2011. Mixing high-speed jets with propeller planes worries Mark Courtney, manager of Lynchburg Regional Airport in Virginia.
"The safety margin begins to narrow," Courtney said. US Airways runs six flights a day between Lynchburg and Charlotte on 50-seat airplanes. The Lynchburg tower is to close May 5, but Courtney is working to find local funding to keep it open.
Although nearly 400 airplanes have collided around non-towered airports since 1982, killing 223 people and seriously injuring 80, safety investigators rarely blame the absence of air-traffic controllers. It's almost impossible to prove that a controller would have kept two airplanes apart - a point highlighted by the 241 collisions at towered airports.
National Transportation Safety Board (NTSB) investigations often cite the failure of two pilots to see each other when airplanes collide in daylight near non-towered airports.
In January 2008, two Cessnas collided on a perpendicular angle near Corona Municipal Airport in Southern California as one airplane was descending to land while the other was ascending after takeoff. The collision killed all four people in the planes and a fifth person on the ground, hit by falling airplane debris.
A similar perpendicular collision occurred in February 2010 over Boulder, Colo., killing the pilot and a passenger in a Cirrus airplane that smashed into a Piper, whose pilot also was killed. The NTSB said the pilots would have had trouble seeing the other airplanes because the white Cirrus blended into the overcast sky. The Piper was set against terrain and Boulder's cityscape.
In July 2012, a 73-year-old pilot landing in Valentine, Neb., accidentally hit the airplane of his friend and flying companion who had landed moments earlier and was on the runway. The friend, Joseph Andrews Jr. of Puyallup, Wash., died from the crash injuries three weeks later. Surviving pilot Harold Smith said he hadn't seen Andrews steer his airplane to the side of the runway.
"This accident leaves me with a very heavy heart which will be with me for many years," Smith wrote in a statement to the NTSB.
Pilots flying in and out of non-towered airports are supposed to fly within established traffic lanes, announce their position using an airport radio channel, and avoid flying in poor visibility unless they are qualified to fly using navigation instruments and have FAA clearance.
Those guidelines are often broken, particularly at non-towered airports, said Gene Benson, an aviation-safety consultant in Hilton, N.Y.
"These airports are magnets for aircraft flying without operating radios," Benson said, noting that the practice is usually legal. Some pilots fly outside traffic patterns, or in bad visibility when they shouldn't. "Not everybody does what they're trained to do in flight school," Benson said.
Airport controllers can enforce rules and can notify arriving pilots of runway hazards such as wildlife or a slippery surface. "I've been coming in many times and the controller will say, I see three deer or a flock of geese," Benson said.
On Thursday, the Texas Department of Transportation agreed to pay $2 million to keep open 13 airport towers in the state and a tower in Texarkana, Ark., for 90 days while officials seek a long-term funding source. The airports handle 1,100 flights a week on average.
"The FAA made a determination that we should have the control towers here for the past decade or longer," DOT executive director Phil Wilson said. "We're trying to maintain that level of safety and integrity."