WASHINGTON (AP) _ Weeks after government auditors said the Federal Aviation Administration was falling behind in efforts to get its computers ready for the year 2000, the agency says about 99 percent of its systems have been renovated.

Testing already has begun to make sure the systems are working properly, FAA Administrator Jane Garvey told a joint meeting of two House committees Tuesday.

``Aviation safety will not be compromised on Jan. 1, 2000, or on any other day,'' she said.

Computer programmers inside and outside government are scrambling to avert disasters expected when Jan. 1, 2000, arrives. That's when computer systems performing calculations involving dates may begin generating incorrect data because they recognize only the last two digits of a year and will assume that 2000 is 1900.

The Year 2000, or ``Y2K,'' computer bug could spark anything from power outages, traffic snarls, paycheck delays and disruption of air travel, some experts have said.

Garvey said she's confident that air travel will remain safe. All FAA systems are expected to be tested and Y2K ready by June 1999, she told members of the House Transportation Committee and the House Task Force on Y2K. Most systems will be ready by March 1999.

FAA officials also are turning their attention to monitoring the computer systems of other countries and efforts to update them, she said. Sixty percent of Americans travel to six countries _ Mexico, Japan, Britain, Canada, the Bahamas and the Dominican Republic _ and special work teams have been formed for each one, she said.

In August, the General Accounting Office said it doubted whether the agency could correct its systems adequately before the year 2000 deadline.

Although the FAA had been making progress, it was still falling behind, said Joel C. Willemssen, director of the civil agencies information systems for the General Accounting Office.

FAA spokesman Paul Takemoto said since that time the agency had set new priorities and redoubled its efforts.

Even with the government at optimal readiness, problems will still occur, said Bruce Webster, chief technical officer of the Object System Group and co-chairman of the Washington, D.C., Year 2000 Group. The worldwide network of interacting computer systems is so vast and complex, there's no way to tell exactly what will happen and when.

``I doubt that we can find all the Y2K bugs and fix them,'' he said.

For government computer systems that won't be ready in time, there's a stopgap measure that would have programmers turn the clocks of computers back to 1970, a calendar year identical to 1998. When 2000 arrives, computers would think it was 1972, said consultant David E. Sullivan, president of the ZONAR Corp. Programmers would then have more time to work out their Y2K problems, he added.