The Federal Aviation Administration has claimed a major glitch that grounded dozens of flights last week was caused by a Cold War-vintage reconnaissance aircraft.
It claimed that a U-2 "Dragon Lady" flew into airspace controlled by the Los Angeles Air Route Traffic Control Center in Palmdale, which uses a system called En Route Automation Modernization (ERAM) to make sure aircraft don't collide in mid-air.
However, ERAM incorrectly assessed the altitude of the U-2, which was flying at 60,000 feet, and decided to shut itself down.
After the meltdown on April 30, ten flights were cancelled at Los Angeles International Airport (LAX) and a total of about 500 flights were delayed.
The FAA has tried to reassure anxious passengers that the glitch was caused by a simple error. It spoke out yesterday after a weekend of frenzied speculation.
In a statement, the FAA suggested “the computer system interpreted the flight as a more typical low-altitude operation and began processing it for a route below 10,000 feet”.
The sheer complexity involved in steering the U-2 around so many other aircraft at that low altitude caused ERAM to crumble.
"The extensive number of routings that would have been required to de-conflict the aircraft with lower-altitude flights used a large amount of available memory and interrupted the computer’s other flight-processing functions,” the FAA continued.
The US Air Force's Air Combat Command told Air Force Times that a U-2 was flying a "routine training mission" from Beale Air Force Base, California.
A further statement from the FAA claimed that technicians had “resolved the specific issue that triggered the problem” but without going into detail.
"There was a U-2 operating in the area in accordance with all FAA regulations. It filed a flight plan. It was conducting a training operation," said Army Colonel Steve Warren, a Pentagon spokesman. He claimed it was not out of the ordinary for a spy plane to be zooming over the affected airport and added:
"The U-2 filed all the proper flight plan paperwork and was conducting its operation in accordance with those filings."
The system shutdown caused a total of 50 flight cancellations and 455 delays. Bob Hope Airport in Burbank, California, John Wayne Airport in Santa Ana, California, and McCarran International Airport in Las Vegas were also affected.
The U-2 has been flown by the US, under the authority of various agencies including the USAF and the CIA, since its first test flight in 1955. The aircraft's secret intelligence-gathering operations were explosively blown into the public domain after a CIA-operated U-2 flight over the USSR, piloted by ex-USAF captain Gary Powers, was shot down by the Soviets in 1960 with Powers being captured alive.
The US still operates the U-2 to this day, although rumours gather that the elderly airframes are due to be retired and replaced.
ERAM is a $2.1bn scheme to overhaul the systems which help air traffic controllers manage high altitude flights. It started in 2002 and was supposed to be installed in 20 "en route" facilities by 2010. However, software problems were identified [PDF] and this goal was not met.
These concerns were raised in an audit report produced by the Office of the Inspector General, which warned that the "multibillion dollar ERAM program has experienced software problems that have impacted the system’s ability to safely manage and separate aircraft". ®