Research Paper
The North-South Airline* In 2008, Northern Airlines* merged with Southeast Airlines to create the fourth largest U.S. carrier. The new North-South Airline inherited both an aging fleet of Boeing 737—200 aircraft and Stephen Ruth. Ruth was a tough former secretary of the navy who stepped in as new president and chairman of the board.
Ruth’s first concern in creating a financially solid company was maintenance costs. It was commonly believed in the airline industry that maintenance costs rose with the age of the aircraft. Ruth quickly noticed that, historically, there has been a significant difference in reported B737—200 maintenance costs (from ATA Form 41s) both in the airframe and engine areas between Northern Airlines and Southeast Airlines, with Southeast having the newer fleet.
On November 12, 2008, Ruth assigned Peg Young, vice president for operations and maintenance, to study the issue. Specifically, Ruth wanted to know (1) whether the average fleet age was correlated to direct airframe maintenance costs and (2) whether there was a relationship between average fleet age and direct engine maintenance costs. Young was to report back with the answer, along with quantitative and graphical descriptions of the relationship, by November 26.
First, Young had her staff construct the average age of Northern and Southeast B737-200 fleets, by quarter, since the introduction of the aircraft to service by each airline in late 1999 and early 2000. The average age of each fleet was calculated by first multiplying the total number of calendar days that each aircraft had been in service at the pertinent point in time by the average daily utilization of the respective fleet to total fleet-hours flown. The total fleet-hours flown was then divided by the number of aircraft in service at that time, giving the age of the "average" aircraft in the fleet.
The average utilization was found by taking the actual total fleet-hours flown at September 30, 2008, from
Ruth’s first concern in creating a financially solid company was maintenance costs. It was commonly believed in the airline industry that maintenance costs rose with the age of the aircraft. Ruth quickly noticed that, historically, there has been a significant difference in reported B737—200 maintenance costs (from ATA Form 41s) both in the airframe and engine areas between Northern Airlines and Southeast Airlines, with Southeast having the newer fleet.
On November 12, 2008, Ruth assigned Peg Young, vice president for operations and maintenance, to study the issue. Specifically, Ruth wanted to know (1) whether the average fleet age was correlated to direct airframe maintenance costs and (2) whether there was a relationship between average fleet age and direct engine maintenance costs. Young was to report back with the answer, along with quantitative and graphical descriptions of the relationship, by November 26.
First, Young had her staff construct the average age of Northern and Southeast B737-200 fleets, by quarter, since the introduction of the aircraft to service by each airline in late 1999 and early 2000. The average age of each fleet was calculated by first multiplying the total number of calendar days that each aircraft had been in service at the pertinent point in time by the average daily utilization of the respective fleet to total fleet-hours flown. The total fleet-hours flown was then divided by the number of aircraft in service at that time, giving the age of the "average" aircraft in the fleet.
The average utilization was found by taking the actual total fleet-hours flown at September 30, 2008, from