Specifically, it could fly off of a carrier deck, and with a tracking capacity of over 250 targets it was well suited to warn the ships and planes of a carrier battle group of any activity that might pose a threat to their operations.

The Yemeni Government, in the northern capital, Sana, has declared the coast and airspace around Aden and the southern coast a military zone and warned ships and planes to stay out.

The north has since warned foreign ships and planes to avoid southern "war zones."

The equipment, called Doppler weather radar systems, will allow air controllers to warn planes of hazardous wind shear conditions.

Asked about the board's contention that the F.A.A. was moving too slowly, Laura J. Brown, a spokeswoman for the agency, cited the systems under development that would flash lights to warn incoming planes.

Canada is reviewing its safety practices, including its decision years ago not to install equipment to warn planes of dangerous wind shifts.

Various work shifts bring sunsets and sunrises, day views and nighttime sparkle, including lights blinking atop other tall buildings to warn errant low-flying planes.

Iran, too, may bear responsibility for failing to warn civilian planes away from the combat zone of an action it had initiated.

One plane reported that it was "very, very poor," and a snowplow operator told controllers to be careful to warn planes about his presence because "it's pretty foggy out here."

As a last step he switched off the flashing red anticollision lights, which could be seen for miles and warned other planes of their presence.