A U.S. Air Force panel has concluded that the aging C-5A Galaxy transport fleet can keep flying safely for another quarter century if adequate upgrades are made.

The Air Force Fleet Viability Board (AFFVB) said in a new report that the service's C-5As, which are more than 30 years old, have "no major structural life issues." The board also wrote that the Galaxy, the nation's largest cargo transport, requires "significant maintenance effort and support costs, but nothing that is disproportionate to the enormity of the aircraft itself."

The board found that the C-5A has some mission limitations but most can be resolved if the Air Force invests in avionics improvements and new engines.

"In the [AFFVB's] judgment, with the addition of avionics and engine modifications, the C-5A has at least 25 years of service life remaining and is assessed to be viable," the report says.

While the report appears to be a boost for proponents of keeping the Lockheed Martin aircraft in service, Air Force Secretary James Roche wrote in a July 14 letter presenting key lawmakers with the report that the C-5A's fate will depend on the results of several other reviews, including the Defense Department's Mobility Capability Study, scheduled for completion in November, and future tests of a C-5A that will have gone through the Avionics Modernization Program (AMP) and the Reliability Enhancement and Re-engining Program (RERP).

"Before the Air Force can make a final decision on how long the C-5A fleet will be operated, we will need the results of the Mobility Capability Study, the AMP test, the RERP test, and the complete aircraft teardown analysis that is currently under way at Warner Robins Air Logistics Center" in Georgia, Roche wrote.

While the report indicates the aircraft can remain viable, "there is still a significant cost in keeping the C-5A fleet flying," Air Force spokeswoman Jackie Hampton said. The report says that putting the C-5As through AMP and RERP would cost $3 billion.

The Air Force set up the board to examine whether the service should sustain or retire aging aircraft. The C-5A review, which began last October, is considered the prototype process.

The C-5A was built from 1968 to 1973. It has had "significant reliability and maintainability issues" for most of its life, but its performance has generally improved over time, the board's report says. For instance, the mission capable rate has risen from the 40 percent range in the 1970s to 75 percent today.

The report also says the AMP and RERP programs "will correct the aircraft's most troublesome problems to the point where the aircraft will have substantially improved reliability, maintainability, capability and service life." The board said another avionics upgrade would probably be needed in fiscal 2020 "to keep pace with emerging requirements, technologies and procedures or face mission limitations."

The Air Force has 70 C-5As, 10 of which are slated for retirement by FY '05.