WASHINGTON (AP) _ The National Mediation Board today called an ``exploration meeting'' to bring Northwest Airlines officials and union leaders back to the table to identify areas of flexibility as the pilots' strike entered its fifth day.

Both parties indicated there was room for negotiation in their Tuesday meeting with Transportation Secretary Rodney Slater, said mediation board spokesman Jim Armshaw. The purpose of the next session, he said, would be to identify the areas of flexibility.

Armshaw said that National Mediation Board member Maggie Jackson was contacting the parties to establish a time and place for what he said was ``an exploration meeting, which could then turn into a negotiation session.''

While Armshaw stressed that this was not a formal bargaining session, deciding to bring the two parties back to the table was a sign of progress.

Dispatchers and meteorologists were the first to go as Northwest began laying off other employees in the fifth day of the pilots' strike.

The company laid off 177 workers Tuesday and was to decide today whether more would have to leave. Company officials said many of Northwest's 50,000 employees could be affected.

``Laying off flight attendants is only going to make it more difficult for the company to get back on its feet quickly,'' said Craig Merrilees, a spokesman for the flight attendants' 11,000-member Teamsters Local 2000.

Robert Lattery, a meteorologist at Northwest's Twin Cities hub, said he received his notice after his overnight shift ended at 8 a.m. He wasn't surprised, since his job is to tell pilots where bad weather is located so planes can avoid thunderstorms and other turbulence.

The employees were told they will not be paid for time lost and they are not to report for work until called back by the airline.

``We had been expecting this,'' Lattery said. ``I was there last night and there was little or nothing to do.''

Lattery, who has worked for Northwest for 13 years, said he supported the pilots.

``Whatever they're able to get will filter down to the rest of the unions in the same form or something similar,'' he said.

Transportation Secretary Rodney Slater, who met Tuesday with Northwest Airlines chief executive John Dasburg and union leaders, said he reiterated President Clinton's desire for settlement without federal intervention.

``I emphasized to both parties the president's concern about the impact that this strike is having on the economy of specific regions of this country and upon the flying public,'' he said.

Northwest spokeswoman Marta Laughlin said the company ``appreciated the opportunity to explain our position,'' but had no further comment on the meeting.

``The meeting was productive,'' said J. Randolph Babbitt, president of the Air Line Pilots Association.

The two sides are separated on issues of compensation and job security.

Northwest is the nation's sixth-largest airline in terms of passengers carried annually and the fourth-largest in revenue. It carries nearly 150,000 passengers a day and 2.9 million pounds of cargo on 1,700 flights in North America, Europe, Asia and India.

Also Tuesday night, talks broke down between Air Canada and its 2,100 pilots over issues of pay and working conditions, forcing the airline to cancel all of its flights worldwide.

The strike is the first in the Air Canada Pilots Association's 61-year history. Air Canada carries approximately 60,000 passengers daily.

Priscille LeBlanc, spokeswoman for Air Canada, said no talks were scheduled, and the airline has negotiated agreements with a number of carriers to have Air Canada tickets accepted at face value.