The jet's metallic skin is reportedly the principal cause of its maintenance troubles, with unexpected problems such as vulnerability to rain and other abrasions.
Recent tests have required more than 30 hours of maintenance for every hour of flight, The Washington Post says, quoting government reports. Such maintenance demand is said to push the plane's hourly cost of flying to more than $44,000, far higher than for the warplane it replaces.
Citing figures from last October to May, the U.S. Defense Department says that an average of just 55 percent of the deployed F-22 fleet has been available to fulfill missions guarding U.S. airspace and the advanced aircraft has never been flown over Iraq or Afghanistan.
The fighter's problems are emerging in the middle of a fight between the Obama administration and the Democratic-controlled Congress over whether the program should be halted next year at 187 planes, far short of the total production expected.
The F-22 does have its backers. Some defense officials emphasize the fighter's unsurpassed flying abilities, are optimistic the troubles will abate, and say the plane is worth the unexpected costs.