In the weeks leading up to the recent offensive in Marja, military officials said, several of the 32 remaining U-2s found nearly 150 possible mines in roads and helicopter landing areas, enabling the Marines to blow them up before approaching the town.

Marine officers say they relied on photographs from the U-2’s old film cameras, which take panoramic images at such a high resolution they can see insurgent footpaths, while the U-2’s newer digital cameras beamed back frequent updates on 25 spots where the Marines thought they could be vulnerable.

In addition, the U-2’s altitude, once a defense against antiaircraft missiles, enables it to scoop up signals from insurgent phone conversations that mountains would otherwise block.

As a result, Colonel Brown said, the U-2 is often able to collect information that suggests where to send the Predator and Reaper drones, which take video and also fire missiles. He said the most reliable intelligence comes when the U-2s and the drones are all concentrated over the same area, as is increasingly the case.

The U-2, a black jet with long, narrow wings to help it slip through the thin air, cuts an impressive figure as it rises rapidly into the sky. It flies at twice the height of a commercial jet, affording pilots views of such things as the earth’s curvature.

But the plane, nicknamed the Dragon Lady, is difficult to fly, and missions are grueling and dangerous. The U-2s used in Afghanistan and Iraq commute each day from a base near the Persian Gulf, and the trip can last nine to 12 hours. Pilots eat meals squeezed through tubes and wear spacesuits because their blood would literally boil if they had to eject unprotected at such a high altitude.