Some thoughts on the Air Force’s mobility fleet…. These observations are my own and do not represent official military policy.

Tonight, in Air Force jets over a black Atlantic, bleary-eyed aviators will sip coffee and monitor instruments on the first leg of an airlift run to Afghanistan or Iraq.

They’ll maneuver their C-17s or C-5s in a precise sky ballet to refuel in mid-air from a KC-135 Stratotanker or a KC-10 Extender. If they don’t refuel in the air, they’ll land in Europe for fuel and crew rest. Then they’ll take off again, bound for the war zone, with cargo compartments full of troops, ammunition, medical supplies, Humvee parts, or anything else needed by American forces.

On the return trips, they’ll bring back vehicles needing overhaul, wounded needed treatment, or soldiers rotating home at the end of their tours. This process goes on every day and night, scores of aircraft aloft at any given moment, in what fliers call the “aluminum overcast.”

With the current surge in the Afghanistan war effort, and with the clock ticking toward a planned July 2011 troop phase-down, airlift becomes ever more important. Roughly every two minutes, an Air Mobility Command aircraft takes to the skies. Strategists call it the air bridge. And, like any kind of infrastructure, parts of that air bridge are aging.

Recently I flew a training mission in which my crew’s C-5 Galaxy took fuel from a Stratotanker. For routine paperwork, I wrote down the tanker’s tail number. It started with 59. That’s the year it was built.

Not all mobility aircraft are that geriatric; some C-17 Globemasters still have that new-car smell, and Globemasters continue to roll off the assembly line. So do C-130Js, the latest version of the time-tested C-130 Hercules. But with some other aircraft, tankers in particular, flight crews and maintainers struggle to complete missions with planes older than anyone on board.

The mechanics do a marvelous job, but hard work and ingenuity can go only so far. As any of them will tell you, there are two kinds of machines: those that have broken down and those that are going to. The older the aircraft, the more likely the failure.

Above the pay grades of crew dogs like me, Air Force leaders are working to outfit the fleet with new tankers. According to a recent article in Air Force magazine, the journal of the Air Force Association, a military study has concluded that the U.S. needs 567 aerial tankers to meet current demands. It has only 474, most from the Eisenhower era.

Aerospace manufacturers are now in a contract competition to determine which company will build a new KC-X tanker. Officials plan to announce the contract award sometime this fall. Despite economic uncertainty and huge federal deficits, upgrading the air bridge is a good long-term investment.

In the meantime, traffic across the air bridge isn’t getting any lighter. Even in Afghanistan’s best-case scenario, with trained and competent Afghan soldiers and police taking over from Coalition forces, the Kabul government will still need equipment and supplies from the U.S. The Air Force’s mobility fleet could remain involved in Afghanistan long after the last shot is fired.

Additionally, in both wartime and peacetime, transport aircraft and tankers help resupply embassies, respond to natural disasters–and prepare for the next war. Tankers also support other kinds of flight operations: fighters go fast, but they can’t go far without refueling.

While you read this, and while Congress considers budget priorities, a flight crew is somewhere above you–perhaps in an aircraft their grandfathers could have flown. They have a long night ahead of them, and it’ll get longer if an emergency interrupts their mission. In Baghdad or Kandahar, a logistics officer awaits cargo, maybe something badly needed by soldiers in the field. The fliers are checking their navigation, watching their fuel consumption, and scanning for warning lights, hoping nothing goes wrong.