TRANSPORTATION

. . . But Traffic Down: More on the air transportation front:

Because of the yearlong construction jumble at John Wayne Airport, passenger traffic for the first nine months of 1990 was down 3.2% from the same period in 1989, and the number of takeoffs and landings by big passenger jets was down 2.4%.

In September, however, the passenger count increased 7.1%, to 383,003 from 357,554 a year earlier. The carriers are apparently packing more people on each plane, however, because their total operations for the month were up just 3%.

The big business increase seems to be with the air taxi, or commuter airline, firms. They posted a 19% increase in flight operations in September and a 15.5% increase for the first nine months--24,967 takeoffs and landings versus 21,610 for the first nine months of 1989.

At United Express, the largest commuter carrier at the airport, the September passenger load shot to 10,859, up 50% from 7,234 in September, 1989, and more than double the 4,959 passengers carried in September, 1988.