Northwest Airlines is gearing up after a 109-day strike by its pilots but the process in a slow one.

By Friday, Northwest will have resumed almost three-quarters of the flights it was operating before the strike - it will be operating 143 passenger flights a day compared with about 200 prior to the strike - but it is carrying one-quarter to one-third of the passengers compared with a year ago, according to Roy K. Erickson, a NWO vice president.

Service has been restored to all of the cities it serves in the Orient and most of its North American points except Atlanta; Edmonton, Canada; Fort Lauderdale, Fla.; Hilo, Hawaii; Jamestown, N.D.; Miami; New Orleans; and Tampa/St. Petersburg. Fla. The airline plans to restore those points next month.

The cities that are being served geuerally are not getting the same number of flights now as before the strike, however. "Our program is to restore servie as quickly as we can to all of the cities that we serve and then to add frequencies as our traffic builds," Erickson said.

"You can imagine the difficulty in coming back after a lengthy strike: you come back with absolutely no advance business on the books," he said.

Flights will be added between cities when the flights already operating are breaking even, he noted.

Northwest, considered an efficient airline with low costs, began to make money in 1977 after 44 percent of its seats were filled. So far in the three weeks since it began restoring service, its highest load fatcor was 47 percent on Aug. 31. In recent days, it filled between 32 and 45 percent of its seats each day.

Northwest, considered an efficient airline with low costs, began to make money in 1977 after 44 percent of its seats were filled. So far, in the three weeks since it began restoring service, its highest load factor was 47 percent on Aug. 31. In recent days, it filled between 32 and 45 percent of its seats each day.

Erickson said restoration of service has been complicated by the unwillingness of the pilots to sign a back-to-work agreement - something they agreed to at the end of a 95-day strike in 1972 - giving Northwest more flexibility in calling back workers out of seniority.

One of the casualties of the lengthy strike is NWO's newly authorized European services, at least for now.

In order to attract passengers back to NWO, the airline got Civil Aeronautics Board permission to waive the 30-day advance purchase requirement on Super Saver fares for travel commencing through Sept. 24.