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The Mobility Metric Quandary


November 25, 2008—
Will the Defense Department include in its upcoming Mobility Capabilities Study the long-used mobility yardstick that it eschewed in the last MCS? The million ton miles per day measure had been used to determine required capability for at least 45 years; Congress noted its absence in the previous MCS (released in December 2005) and told DOD to put it back. The MTM/D metric was used in the previous study—Mobility Requirements Study-2005—which found that US airlift capacity was short of the needed 54.5 MTM/D. But the MRS-05 was conducted prior to the terrorist attacks of 9/11, and Air Force officials subsequently said that the requirement had gone up to more than 60 MTM/D based on current operations tempo. (See Rising Risk in Air Mobility) However, the December 2005 MCS (sans the MTM/D metric and, some say, done with little Air Force mobility input) declared that the US had sufficient airlift capacity and could cap the C-17 purchase at 180 aircraft. Lawmakers disagreed, providing more money for additional C-17s and instructing DOD to conduct new mobility studies, one by an independent entity due in January 2009 and one by the Pentagon in May 2009. According to a new Government Accountability Office report, which cautions against premature shutdown of the C-17 production line and suggests that the Air Force may still have underestimated the cost of C-5 upgrades, some defense analysts "expect the [two new] studies will identify increased demands on airlift." The GAO was able to elicit MTM/D estimates (shown here) from DOD as the numbers of C-5s and C-17s has fluctuated over the past three years, still the Congressional watchdog agency apparently hasn't been able to pin down the metrics to be used in either of the new studies. Despite DOD's assurance, in response to the GAO report, that it plans to use "appropriate metrics (to include ton-miles per day)," a US Transportation Command official told GAO a decision on metrics had not been made.