Marine Corps Commandant James Conway warned that the Marine Corps "will not buy a vehicle that's 20,000 lb." Requirements called for the cabin heater to raise the crew compartment temperature from to in one hour. The air-conditioner should drop the temperature from to within forty minutes. The JLTV was to be equipped with a diagnostic monitoring system that will electronically alert the operator of equipment failures so that they can be fixed. The electronic monitoring will observe the fuel, air intake, engine, cooling, transmission, energy storage, power generation and vehicle speed as well as other systems. Mobility The Pentagon required at least 600 mean miles before an essential function failure. The vehicle was to be capable of traveling for 3 miles (5 km) cross-country having endured three perforations of half-full main fuel tanks. The JLTV must also operate in altitudes from minus 500 feet to 12,000 feet and maintain full mission capability in temperatures from , according to established requirements. When temperatures drop well below zero, the JLTV must start within one minute with no external aids, kits or prior warming of the batteries. The vehicle must be capable of traveling paved at or in operational terrain on a single tank of JP-8 fuel. Acceleration from in 9.7 seconds on dry, level, hard terrain was required as a threshold requirement (objective being 7 seconds), as was the ability to ford of saltwater without a fording kit, in forward and reverse, while maintaining contact with the ground. Other tactically driven mobility requirements include a threshold 27-foot turning radius and the ability to climb 24-inch vertical obstacles in forward and reverse. JLTV must be able to drive off an 18-inch vertical step at 15 mph and sustain no mechanical damage. It will be capable of traversing a 20-degree V-ditch that is 25 feet wide at an approach angle of 45-degree. It can 'jump' a 6-inch parallel curb at 15 mph and traverse a 20-foot flight of stairs at 5 mph. It must climb a 60 percent dry, hard-surfaced gradient and traverse a 40 percent sideslope with no degradation in driver control. JLTV is transportable by sea, rail, and air. The JLTV is transportable on all classes of ocean-going transport ships with minimal disassembly. It was required to be rail-transportable on U.S. and NATO country railways. Air transportability will be by fixed-wing aircraft as large or larger than the C-130 Hercules and sling-loadable