SINGAPORE – The airplane carrying Defense Secretary Robert Gates and his team to Southeast Asia and back has not cooperated for its planned six-day tour of Singapore, the Philippines and Alaska.

The trip to Singapore was delayed by a half day due to aircraft troubles that were supposed to be fixed before the next leg began.

But this is no ordinary airplane.It is the E-4B, a converted Boeing 747-200 built in 1979 that is considered the secretary’s version of Air Force One. It contains a mobile command center and is prepared to survive nuclear war.

And now it may have sputtered out.

On Sunday, as a traveling entourage of officials, aides and press were about to head for the airport to depart for the Philippines, already several hours behind schedule, the party was sent back into the hotel. Then word came: the flight was canceled.

Pentagon press secretary Geoff Morrell released this statement: "Secretary Gates has elected to delay by a day his travel to Manila. A series of mechanical problems on one of the military’s specially-outfitted 747’s prevented it from being flown today as scheduled. The flight crew is hard at work trying to repair the aircraft, but a back-up plane with appropriate communications capabilities is being flown into Singapore and will be available to transport the secretary to Manila Monday morning if needed.

“Despite the later arrival, the Secretary still anticipates being able to conduct all of his planned engagements in Manila, including meeting with Secretary of National Defense Gilberto Teodoro and visiting with US and Philippine forces, before heading to Alaska."

An Air Force fact sheet estimates, taking inflation into consideration, the E-4B costs more than $220 million. Onboard is the National Airborne Operations Center, one of four flying military command centers available to the president, secretary and the chairman of the Joint Chiefs of Staff.

But this E-4B is the only one operating on full-time alert.

According to an Air Force Web site, “In case of national emergency or destruction of ground command control centers, the aircraft provides a highly survivable, command, control and communications center to direct U.S. forces, execute emergency war orders and coordinate actions by civil authorities.”

The plane troubles come while the secretary is traveling through Asia during a week in which North Korea has detonated an underground nuclear explosion, launched several missiles of varying ranges, in defiance of international agreements and condemnations, and reportedly is moving a long-range missile for another possible test flight.

Maintenance of the secretary’s plane is the responsibility of Air Combat Command, while operations are the responsibility of the Joint Chiefs of Staff through the U.S. Strategic Command, or USSTRATCOM, the Web site says.

The jet’s aftermarket modifications include wartime protections such as “nuclear and thermal effects shielding”, and “electromagnetic pulse protection,” earning its nickname, the “Doomsday plane.” It has four engines capable of 52,500 pounds of thrust and a swept wingspan of 231 feet. It can fly at high-altitudes and is fitted for in-flight refueling (410,000 gallons worth).

The aircraft also has special communications abilities and room for a crew of to 112 people.

Officials would not divulge for the record the specific technical difficulties. But the problems caused an hours-long delay before departing the United States from Kansas, where Gates was attending his high school reunion, and forced what was supposed to be a 20-hour nonstop flight to Singapore into an old-fashioned island hop-scotch across the Pacific via Hawaii and Guam.

After two days in Singapore, the E-4B still was not up to necessary standards, causing Gates to miss scheduled events on Sunday in Manila.

Gates came to Singapore to address the Shangri-La Dialogue, a conference of regional defense ministers and officials hosted by the International Institute for Security Studies, a think tank in London.

His last stop is expected to be in Alaska, where he will visit troops at Elmendorf Air Force Base, near Anchorage.