Ask the Captain: Do planes have quirks like cars?

Question: Owners of cars, trucks and motorcycles, especially older models, learn the quirks of their vehicles and how to safely compensate for them while driving. It made me wonder if flight crews recognize individual planes when their airlines own dozens or hundreds of the same model. Are modern commercial aircraft maintained so precisely that individual airplanes of the same model do not have unique mechanical or electrical quirks that pilots notice in flight? How often do pilots at major airlines fly the exact same (by tail number) airplanes?                   

– John, West Lafayette, Indiana

Answer: Pilots fly many different airplanes of the same model within a fleet. While there are some differences, they fly pretty much the same. Manufacturers strive to produce airplanes that are very similar. 

A pilot will see, on average, the same tail number several a times a year, but it is random rotation. Airplanes rotate through the system flying different routes. The determining factor is often is the maintenance schedule.  

Pilots usually change their trips monthly. The airplanes usually change routes daily. 

Airplanes fly pretty much the same with limited “quirks,” but some specific tail numbers handle slightly differently. This can be caused by it being older and having had major maintenance on flight controls. If it has had a very hard landing requiring repair, it will fly slightly differently, like a car that has been repaired after an accident. 

Q: Why do some airlines have similar planes? I believe Delta is buying both the A321 and the 737-900 ER, both with similar capability for 180 passengers and 2,500 miles. I would have thought standardizing on just one would have benefits.  

– Peter Higgins, Melbourne, Florida

A: There are several reasons why airlines will fly similar airplanes. When negotiating the purchase price, the airline can often get better pricing by pitting one manufacturer against another. When each manufacturer knows it is possible that the other might get the purchase order, there is a strong incentive to lower the price.

Often a large airline will want to introduce a new airplane more rapidly than a manufacturer can produce it. If the airline is receiving new airplanes from more than one source, it can introduce them faster, allowing for retirement of older, less efficient models.

Finally, there are nuances between similar models that airlines can use to their advantage. While the A320 family and the B737 family look very similar, each has strengths and weaknesses. As an example, one type may have more payload capability at sea level and another have more payload capability at a high mountainous airport. Careful scheduling allows an airline to maximize those benefits.

Some airlines have kept a single fleet type very successfully. This does lower maintenance and training cost. So there are benefits to both.

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.