Primary variables | Secondary variables | Coding principles |
Time | Year | 1—2015, 2—2016, 3—2017, 4—2018, 5—2019 |
Season* | 1—Winter-Spring, 2—Summer-Autumn | |
Quarter | 1—1st quarter, 2—2nd quarter, 3—3rd quarter, 4—4th quarter | |
Monthly | 1—January, 2—February, 3—March, 4—April, 5—May, 6—June, 7—July, 8—August, 9—September, 10—October, 11—November, 12—December | |
Complaint against | 1—Domestic airline, 2—Foreign airline. | |
Type of complaint | 1—Flight problems, 2—Fare problems, 3—Baggage problems, 4—Check-in problems, 5—Airline problems, 6—Over-selling problems, 7—Special services, 8—Cargo problems, 9—Other problems |