First of all Mechanics were hired as the fleet increased.
You forget a new facility was opened in 1990 in Charlotte and the place had to be staffed. Also the TPA hangar was built and had to be staffed as was IND Hangar.
Piedmont and US Airways both had Utility, PI only in a few cities, there was an increase of headcount due to increase of flying. European and Carribean expansion.
But since 1989 there has been lots of facilities closed, SAN (hangar and engine shop) UCA heavy Maintenance, INT heavy maintenance, GSO hangar, IND Hangar, ROA Hangar, BUF Hangar, CLE Hangar, DCA hanger closed and now reopened, MIA Hangar, ILM Hangar, and TPA hangar.
Maintenance stations have been closed since 1992 also, US is down to 18 maintenance stations from a high of 30+.
The maintenance department has been cut by almost half since the closing of INT, GSO, ROA, TPA and 9/11.
So maintenance has been hit very hard, there are more mechanic and related on furlough then pilots.
Where do we go from here, who knows, but you won't get 50% of the workforce to vote themselves out of a job.