Things are looking up for flexitime, the program that allows nearly half a million U.S. employes -- from scientists and clerks to law enforcement types -- to work flexible tours or put in 10-hour days and work four-day weeks.

The Senate yesterday passed (93 to 2) and sent to the House legislation to extend permanently the federal AWS (alternate work schedule) experiment that is due to expire next month.

The House is expected to approve the bill, sponsored by Sen. Ted Stevens (R-Alaska), when it returns July 12 from the Independence Day recess. Otherwise the authority to allow employes to work four-day weeks will expire July 21.

Under the AWS experiment, begun a little over three years ago, thousands of government aides from Washington to Honolulu have gone to flexible work schedules, compressed workweeks and other variations of the traditional eight-hour day.

AWS almost ended in April. But Congress voted a 90-day extension to work out a compromise with the Reagan administration. The White House wants more management control over the program.

The bill that sailed through the GOP-dominated Senate yesterday appears to have the White House stamp of approval, and to meet minimum requirements demanded by the Democratic-controlled House.

Stevens' bill -- similar to the plan by Rep. Geraldine Ferraro (D-N.Y.) -- gives agency heads authority to terminate most existing AWS programs within 90 days. But it also gives unions the right to return to the bargaining table to propose AWS replacements.

The flexitime programs have proved popular with most workers, and supporters say it has reduced tardiness and has improved morale and service to the public.

On the downside, critics say flexible work schedules are more subject to abuse. The General Services Administration dropped most flexitime schedules earlier this year, reportedly because top boss Gerald Carmen said that when he called or visited some offices on flexitime there was nobody minding the store.

The major stumbling block to timely approval of a permanent AWS bill was eliminated yesterday. The Senate rejected a proposed amendment by Sen. William Armstrong (R-Colo). He wanted to extend the voluntary waiver of overtime after an eight-hour day to private contractors doing business with Uncle Sam.

To avoid overtime the AWS program authorizes employes who put in 10-hour day, four-day weeks waive their normal right overtime for work in excess of an eight-hour day.

Organized labor opposed the Armstrong amendment and warned it would fight the federal AWS program in the House if the waiver of overtime was extended to contractors. Insiders believe the Stevens bill will be approved by the House before the July deadline.

When and if it is approved, federal agency heads will have 90 days to cancel or modify most existing AWS programs. Unions then can begin bargaining for replacement schedules. If the parties fail to agree, the Federal Services Impasses Panel will decide who wins.

If the bill doesn't become law by late July, however, agencies working four-day week shifts will have to put employes back on the eight-hour day, five-day week to avoid overtime.

The AWS program isn't out of the legislative woods yet. But it is on the right track in its race against the calendar.