WASHINGTON — Thirteen years after the 9/11 attacks, military aircraft are scrambling more than once a week, on average, to intercept civilian planes that stray into restricted airspace, military statistics show.
The cost to taxpayers for protecting restricted airspace and the 75 annual diversions runs into the million of dollars.
The number of incidents has decreased in recent years as the military has spread the word to recreational pilots about restricted airspace, according to the North American Aerospace Defense Command (NORAD), the military agency responsible for protecting American airspace.
The agency anticipates that the frequency of intercepts will remain at this level in the future because no amount of outreach will prevent all pilots from straying.
Many recreational pilots fly from small airstrips without a control tower and aren't required to file flight plans. Often they are not aware when a temporary restriction is established.
"They just take off and do what they want," said Steven Armstrong, a NORAD official.
After the Sept. 11, 2001, terrorist attacks, the military boosted its alert facilities around the country, where fighter pilots maintained a round-the-clock state of readiness.
The government has restricted airspace around Washington, D.C., and other sensitive areas, such as some military bases and critical infrastructure. It also frequently sets up temporary restrictions on airspace to protect the president when he flies domestically or during special events, such as the Superbowl.
At its post 9/11 peak, NORAD maintained some 26 alert facilities around the country. The number has shrunk since then, but the agency declined to release the precise number for security reasons.
"We think we're at the minimum to be able to protect the major metropolitan areas and the critical infrastructure," Armstrong said.
It's an expensive enterprise. It costs from $10,000 to $20,000 per flight hour to operate fighters. Alert facilities cost about $7 million a year to operate. The intercept missions in the continental United States are performed by the Air National Guard.
The military uses fighter planes, and, in some locations, helicopters to intercept an aircraft straying into restricted areas.
The pilots have a protocol for engaging with civilian pilots, who are often flying small, propeller-driven aircraft, to divert them out of restricted space.
If NORAD notices an aircraft flying toward restricted space, it will try to contact the pilot by radio before launching an aircraft. NORAD said it follows about 1,800 "tracks of interest" per year. Most of the recreational pilots are diverted before jets have to be scrambled.
If officials are unable to contact a pilot whose plane is heading toward restricted space, NORAD will launch military aircraft that will fly alongside the plane and rock its wings, a signal for the civilian pilot to follow the fighter.
If that doesn't work, fighter planes will often pull in front of the aircraft in a maneuver known as a "head butt" and drop flares to get their attention.
That doesn't always work either. "Sometimes they say that they don't see us," Armstrong said. "Other times, they are just so scared to have a fighter aircraft in that close proximity to them that they kind of panic."
Once they land, pilots are usually met by local law enforcement officials and Secret Service agents, said Craig Spence, an official with the Aircraft Owners and Pilots Association.
"Unfortunately, there is very little sympathy on the part of the local law enforcement and the federal (officials)," Spence said.
The pilots rarely face criminal charges, but the Federal Aviation Administration often suspends a pilot's license for such infractions.
"None of incidents have been threats," Spence said. "The majority of the folks who violate do so not knowing a (temporary restricted area) has been put in place."